Natural gas liquefaction

ABSTRACT

A process for liquefying natural gas in conjunction with producing a liquid stream containing predominantly hydrocarbons heavier than methane is disclosed. In the process, the natural gas stream to be liquefied is partially cooled, expanded to an intermediate pressure, and supplied to a distillation column. The bottom product from this distillation column preferentially contains the majority of any hydrocarbons heavier than methane that would otherwise reduce the purity of the liquefied natural gas. The residual gas stream from the distillation column is compressed to a higher intermediate pressure, cooled under pressure to condense it, and then expanded to low pressure to form the liquefied natural gas stream.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a divisional of U.S. patent application Ser. No.10/161,780, filed on Jun. 4, 2002, which claims priority under 35 U.S.C.§ 199(e) to U.S. Provisional Patent Application No. 60/296,848, filed onJun. 8, 2001.

BACKGROUND OF THE INVENTION

[0002] This invention relates to a process for processing natural gas orother methane-rich gas streams to produce a liquefied natural gas (LNG)stream that has a high methane purity and a liquid stream containingpredominantly hydrocarbons heavier than methane. The applicants claimthe benefits under Title 35, United States Code, Section 119(e) of priorU.S. provisional application Serial No. 60/296,848 which was filed onJun. 8, 2001.

[0003] Natural gas is typically recovered from wells drilled intounderground reservoirs. It usually has a major proportion of methane,i.e., methane comprises at least 50 mole percent of the gas. Dependingon the particular underground reservoir, the natural gas also containsrelatively lesser amounts of heavier hydrocarbons such as ethane,propane, butanes, pentanes and the like, as well as water, hydrogen,nitrogen, carbon dioxide, and other gases.

[0004] Most natural gas is handled in gaseous form. The most commonmeans for transporting natural gas from the wellhead to gas processingplants and thence to the natural gas consumers is in high pressure gastransmission pipelines. In a number of circumstances, however, it hasbeen found necessary and/or desirable to liquefy the natural gas eitherfor transport or for use. In remote locations, for instance, there isoften no pipeline infrastructure that would allow for convenienttransportation of the natural gas to market. In such cases, the muchlower specific volume of LNG relative to natural gas in the gaseousstate can greatly reduce transportation costs by allowing delivery ofthe LNG using cargo ships and transport trucks.

[0005] Another circumstance that favors the liquefaction of natural gasis for its use as a motor vehicle fuel. In large metropolitan areas,there are fleets of buses, taxi cabs, and trucks that could be poweredby LNG if there were an economic source of LNG available. SuchLNG-fueled vehicles produce considerably less air pollution due to theclean-burning nature of natural gas when compared to similar vehiclespowered by gasoline and diesel engines which combust higher molecularweight hydrocarbons. In addition, if the LNG is of high purity (i.e.,with a methane purity of 95 mole percent or higher), the amount ofcarbon dioxide (a “greenhouse gas”) produced is considerably less due tothe lower carbon:hydrogen ratio for methane compared to all otherhydrocarbon fuels.

[0006] The present invention is generally concerned with theliquefaction of natural gas while producing as a co-product a liquidstream consisting primarily of hydrocarbons heavier than methane, suchas natural gas liquids (NGL) composed of ethane, propane, butanes, andheavier hydrocarbon components, liquefied petroleum gas (LPG) composedof propane, butanes, and heavier hydrocarbon components, or condensatecomposed of butanes and heavier hydrocarbon components. Producing theco-product liquid stream has two important benefits: the LNG producedhas a high methane purity, and the co-product liquid is a valuableproduct that may be used for many other purposes. A typical analysis ofa natural gas stream to be processed in accordance with this inventionwould be, in approximate mole percent, 84.2% methane, 7.9% ethane andother C₂ components, 4.9% propane and other C₃ components, 1.0%iso-butane, 1.1% normal butane, 0.8% pentanes plus, with the balancemade up of nitrogen and carbon dioxide. Sulfur containing gases are alsosometimes present.

[0007] There are a number of methods known for liquefying natural gas.For instance, see Finn, Adrian J., Grant L. Johnson, and Terry R.Tomlinson, “LNG Technology for Offshore and Mid-Scale Plants”,Proceedings of the Seventy-Ninth Annual Convention of the Gas ProcessorsAssociation, pp. 429-450, Atlanta, Ga., Mar. 13-15, 2000 and Kikkawa,Yoshitsugi, Masaaki Ohishi, and Noriyoshi Nozawa, “Optimize the PowerSystem of Baseload LNG Plant”, Proceedings of the Eightieth AnnualConvention of the Gas Processors Association, San Antonio, Tex., Mar.12-14, 2001 for surveys of a number of such processes. U.S. Pat. Nos.4,445,917; 4,525,185; 4,545,795; 4,755,200; 5,291,736; 5,363,655;5,365,740; 5,600,969; 5,615,561; 5,651,269; 5,755,114; 5,893,274;6,014,869; 6,062,041; 6,119,479; 6,125,653; 6,250,105 B1; 6,269,655 B1;6,272,882 B1; 6,308,531 B1; 6,324,867 B1; and 6,347,532 B1 also describerelevant processes. These methods generally include steps in which thenatural gas is purified (by removing water and troublesome compoundssuch as carbon dioxide and sulfur compounds), cooled, condensed, andexpanded. Cooling and condensation of the natural gas can beaccomplished in many different manners. “Cascade refrigeration” employsheat exchange of the natural gas with several refrigerants havingsuccessively lower boiling points, such as propane, ethane, and methane.As an alternative, this heat exchange can be accomplished using a singlerefrigerant by evaporating the refrigerant at several different pressurelevels. “Multi-component refrigeration” employs heat exchange of thenatural gas with one or more refrigerant fluids composed of severalrefrigerant components in lieu of multiple single-componentrefrigerants. Expansion of the natural gas can be accomplished bothisenthalpically (using Joule-Thomson expansion, for instance) andisentropically (using a work-expansion turbine, for instance).

[0008] Regardless of the method used to liquefy the natural gas stream,it is common to require removal of a significant fraction of thehydrocarbons heavier than methane before the methane-rich stream isliquefied. The reasons for this hydrocarbon removal step are numerous,including the need to control the heating value of the LNG stream, andthe value of these heavier hydrocarbon components as products in theirown right. Unfortunately, little attention has been focused heretoforeon the efficiency of the hydrocarbon removal step.

[0009] In accordance with the present invention, it has been found thatcareful integration of the hydrocarbon removal step into the LNGliquefaction process can produce both LNG and a separate heavierhydrocarbon liquid product using significantly less energy than priorart processes. The present invention, although applicable at lowerpressures, is particularly advantageous when processing feed gases inthe range of 400 to 1500 psia [2,758 to 10,342 kPa(a)] or higher.

[0010] For a better understanding of the present invention, reference ismade to the following examples and drawings. Referring to the drawings:

[0011]FIG. 1 is a flow diagram of a natural gas liquefaction plantadapted for co-production of NGL in accordance with the presentinvention;

[0012]FIG. 2 is a pressure-enthalpy phase diagram for methane used toillustrate the advantages of the present invention over prior artprocesses;

[0013]FIG. 3 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of NGL in accordance withthe present invention;

[0014]FIG. 4 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of LPG in accordance withthe present invention;

[0015]FIG. 5 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of condensate in accordancewith the present invention;

[0016]FIG. 6 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0017]FIG. 7 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0018]FIG. 8 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0019]FIG. 9 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0020]FIG. 10 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0021]FIG. 11 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0022]FIG. 12 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0023]FIG. 13 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0024]FIG. 14 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0025]FIG. 15 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0026]FIG. 16 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0027]FIG. 17 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0028]FIG. 18 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0029]FIG. 19 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention;

[0030]FIG. 20 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention; and

[0031]FIG. 21 is a flow diagram of an alternative natural gasliquefaction plant adapted for co-production of a liquid stream inaccordance with the present invention.

[0032] In the following explanation of the above figures, tables areprovided summarizing flow rates calculated for representative processconditions. In the tables appearing herein, the values for flow rates(in moles per hour) have been rounded to the nearest whole number forconvenience. The total stream rates shown in the tables include allnon-hydrocarbon components and hence are generally larger than the sumof the stream flow rates for the hydrocarbon components. Temperaturesindicated are approximate values rounded to the nearest degree. Itshould also be noted that the process design calculations performed forthe purpose of comparing the processes depicted in the figures are basedon the assumption of no heat leak from (or to) the surroundings to (orfrom) the process. The quality of commercially available insulatingmaterials makes this a very reasonable assumption and one that istypically made by those skilled in the art.

[0033] For convenience, process parameters are reported in both thetraditional British units and in the units of the International Systemof Units (SI). The molar flow rates given in the tables may beinterpreted as either pound moles per hour or kilogram moles per hour.The energy consumptions reported as horsepower (HP) and/or thousandBritish Thermal Units per hour (MBTU/Hr) correspond to the stated molarflow rates in pound moles per hour. The energy consumptions reported askilowatts (kW) correspond to the stated molar flow rates in kilogrammoles per hour. The production rates reported as pounds per hour (Lb/Hr)correspond to the stated molar flow rates in pound moles per hour. Theproduction rates reported as kilograms per hour (kg/Hr) correspond tothe stated molar flow rates in kilogram moles per hour.

DESCRIPTION OF THE INVENTION EXAMPLE 1

[0034] Referring now to FIG. 1, we begin with an illustration of aprocess in accordance with the present invention where it is desired toproduce an NGL co-product containing the majority of the ethane andheavier components in the natural gas feed stream. In this simulation ofthe present invention, inlet gas enters the plant at 90° F. [32° C.] and1285 psia [8,860 kPa(a)] as stream 31. If the inlet gas contains aconcentration of carbon dioxide and/or sulfur compounds which wouldprevent the product streams from meeting specifications, these compoundsare removed by appropriate pretreatment of the feed gas (notillustrated). In addition, the feed stream is usually dehydrated toprevent hydrate (ice) formation under cryogenic conditions. Soliddesiccant has typically been used for this purpose.

[0035] The feed stream 31 is cooled in heat exchanger 10 by heatexchange with refrigerant streams and demethanizer side reboiler liquidsat −68° F. [−55° C.] (stream 40). Note that in all cases heat exchanger10 is representative of either a multitude of individual heat exchangersor a single multi-pass heat exchanger, or any combination thereof. (Thedecision as to whether to use more than one heat exchanger for theindicated cooling services will depend on a number of factors including,but not limited to, inlet gas flow rate, heat exchanger size, streamtemperatures, etc.) The cooled stream 31 a enters separator 11 at −30°F. [−34° C.] and 1278 psia [8,812 kPa(a)] where the vapor (stream 32) isseparated from the condensed liquid (stream 33).

[0036] The vapor (stream 32) from separator 11 is divided into twostreams, 34 and 36. Stream 34, containing about 20% of the total vapor,is combined with the condensed liquid, stream 33, to form stream 35.Combined stream 35 passes through heat exchanger 13 in heat exchangerelation with refrigerant stream 71 e, resulting in cooling andsubstantial condensation of stream 35 a. The substantially condensedstream 35 a at −120° F. [−85° C.] is then flash expanded through anappropriate expansion device, such as expansion valve 14, to theoperating pressure (approximately 465 psia [3,206 kPa(a)]) offractionation tower 19. During expansion a portion of the stream isvaporized, resulting in cooling of the total stream. In the processillustrated in FIG. 1, the expanded stream 35 b leaving expansion valve14 reaches a temperature of −122° F. [−86° C.], and is supplied at amid-point feed position in demethanizing section 19 b of fractionationtower 19.

[0037] The remaining 80% of the vapor from separator 11 (stream 36)enters a work expansion machine 15 in which mechanical energy isextracted from this portion of the high pressure feed. The machine 15expands the vapor substantially isentropically from a pressure of about1278 psia [8,812 kPa(a)] to the tower operating pressure, with the workexpansion cooling the expanded stream 36 a to a temperature ofapproximately −103° F. [−75° C.]. The typical commercially availableexpanders are capable of recovering on the order of 80-85% of the worktheoretically available in an ideal isentropic expansion. The workrecovered is often used to drive a centrifugal compressor (such as item16) that can be used to re-compress the tower overhead gas (stream 38),for example. The expanded and partially condensed stream 36 a issupplied as feed to distillation column 19 at a lower mid-column feedpoint.

[0038] The demethanizer in fractionation tower 19 is a conventionaldistillation column containing a plurality of vertically spaced trays,one or more packed beds, or some combination of trays and packing. As isoften the case in natural gas processing plants, the fractionation towermay consist of two sections. The upper section 19 a is a separatorwherein the top feed is divided into its respective vapor and liquidportions, and wherein the vapor rising from the lower distillation ordemethanizing section 19 b is combined with the vapor portion (if any)of the top feed to form the cold demethanizer overhead vapor (stream 37)which exits the top of the tower at −135° F. [−93° C.]. The lower,demethanizing section 19 b contains the trays and/or packing andprovides the necessary contact between the liquids falling downward andthe vapors rising upward. The demethanizing section also includes one ormore reboilers (such as reboiler 20) which heat and vaporize a portionof the liquids flowing down the column to provide the stripping vaporswhich flow up the column. The liquid product stream 41 exits the bottomof the tower at 115° F. [46° C.], based on a typical specification of amethane to ethane ratio of 0.020:1 on a molar basis in the bottomproduct.

[0039] The demethanizer overhead vapor (stream 37) is warmed to 90° F.[32° C.] in heat exchanger 24, and a portion of the warmed demethanizeroverhead vapor is withdrawn to serve as fuel gas (stream 48) for theplant. (The amount of fuel gas that must be withdrawn is largelydetermined by the fuel required for the engines and/or turbines drivingthe gas compressors in the plant, such as refrigerant compressors 64,66, and 68 in this example.) The remainder of the warmed demethanizeroverhead vapor (stream 38) is compressed by compressor 16 driven byexpansion machines 15, 61, and 63. After cooling to 100° F. [38° C.] indischarge cooler 25, stream 38 b is further cooled to −123° F. [−86° C.]in heat exchanger 24 by cross exchange with the cold demethanizeroverhead vapor, stream 37.

[0040] Stream 38 c then enters heat exchanger 60 and is further cooledby refrigerant stream 71 d. After cooling to an intermediatetemperature, stream 38 c is divided into two portions. The firstportion, stream 49, is further cooled in heat exchanger 60 to −257° F.[−160° C.] to condense and subcool it, whereupon it enters a workexpansion machine 61 in which mechanical energy is extracted from thestream. The machine 61 expands liquid stream 49 substantiallyisentropically from a pressure of about 562 psia [3,878 kPa(a)] to theLNG storage pressure (15.5 psia [107 kPa(a)]), slightly aboveatmospheric pressure. The work expansion cools the expanded stream 49 ato a temperature of approximately −258° F. [−161° C.], whereupon it isthen directed to the LNG storage tank 62 which holds the LNG product(stream 50). 11 Stream 39, the other portion of stream 38 c, iswithdrawn from heat exchanger 60 at −160° F. [−107° C.] and flashexpanded through an appropriate expansion device, such as expansionvalve 17, to the operating pressure of fractionation tower 19. In theprocess illustrated in FIG. 1, there is no vaporization in expandedstream 39 a, so its temperature drops only slightly to −161° F. [−107°C.] leaving expansion valve 17. The expanded stream 39 a is thensupplied to separator section 19 a in the upper region of fractionationtower 19. The liquids separated therein become the top feed todemethanizing section 19 b.

[0041] All of the cooling for streams 35 and 38 c is provided by aclosed cycle refrigeration loop. The working fluid for this cycle is amixture of hydrocarbons and nitrogen, with the composition of themixture adjusted as needed to provide the required refrigeranttemperature while condensing at a reasonable pressure using theavailable cooling medium. In this case, condensing with cooling waterhas been assumed, so a refrigerant mixture composed of nitrogen,methane, ethane, propane, and heavier hydrocarbons is used in thesimulation of the FIG. 1 process. The composition of the stream, inapproximate mole percent, is 7.5% nitrogen, 41.0% methane, 41.5% ethane,and 10.0% propane, with the balance made up of heavier hydrocarbons.

[0042] The refrigerant stream 71 leaves discharge cooler 69 at 100° F.[38° C.] and 607 psia [4,185 kPa(a)]. It enters heat exchanger 10 and iscooled to −31° F. [−35° C.] and partially condensed by the partiallywarmed expanded refrigerant stream 71 f and by other refrigerantstreams. For the FIG. 1 simulation, it has been assumed that these otherrefrigerant streams are commercial-quality propane refrigerant at threedifferent temperature and pressure levels. The partially condensedrefrigerant stream 71 a then enters heat exchanger 13 for furthercooling to −114° F. [−81 ° C.] by partially warmed expanded refrigerantstream 71 e, condensing and partially subcooling the refrigerant (stream71 b). The refrigerant is further subcooled to −257° F. [−160° C.] inheat exchanger 60 by expanded refrigerant stream 71 d. The subcooledliquid stream 71 c enters a work expansion machine 63 in whichmechanical energy is extracted from the stream as it is expandedsubstantially isentropically from a pressure of about 586 psia [4,040kPa(a)] to about 34 psia [234 kPa(a)]. During expansion a portion of thestream is vaporized, resulting in cooling of the total stream to −263°F. [−164° C.] (stream 71 d). The expanded stream 71 d then reenters heatexchangers 60, 13, and 10 where it provides cooling to stream 38 c,stream 35, and the refrigerant (streams 71, 71 a, and 71 b) as it isvaporized and superheated.

[0043] The superheated refrigerant vapor (stream 71 g) leaves heatexchanger 10 at 93° F. [34° C.] and is compressed in three stages to 617psia [4,254 kPa(a)]. Each of the three compression stages (refrigerantcompressors 64, 66, and 68) is driven by a supplemental power source andis followed by a cooler (discharge coolers 65, 67, and 69) to remove theheat of compression. The compressed stream 71 from discharge cooler 69returns to heat exchanger 10 to complete the cycle.

[0044] A summary of stream flow rates and energy consumption for theprocess illustrated in FIG. 1 is set forth in the following table: TABLEI (FIG. 1) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr] StreamMethane Ethane Propane Butanes+ Total 31 40,977 3,861 2,408 1,404 48,65632 32,360 2,675 1,469 701 37,209 33 8,617 1,186 939 703 11,447 34 6,472535 294 140 7,442 36 25,888 2,140 1,175 561 29,767 37 47,771 223 0 048,000 39 6,867 32 0 0 6,900 41 73 3,670 2,408 1,404 7,556 48 3,168 15 00 3,184 50 37,736 176 0 0 37,916 Recoveries in NGL* Ethane  95.06%Propane 100.00% Butanes+ 100.00% Production Rate 308,147 Lb/Hr [308,147kg/Hr] LNG Product Production Rate 610,813 Lb/Hr [610,813 kg/Hr] Purity* 99.52% Lower Heating Value  912.3 BTU/SCF [33.99 MJ/m³] PowerRefrigerant Compression 103,957 HP [170,904 kW] Propane Compression 33,815 HP [55,591 kW] Total Compression 137,772 HP [226,495 kW] UtilityHeat Demethanizer Reboiler  29,364 MBTU/Hr [18,969 kW]

[0045] The efficiency of LNG production processes is typically comparedusing the “specific power consumption” required, which is the ratio ofthe total refrigeration compression power to the total liquid productionrate. Published information on the specific power consumption for priorart processes for producing LNG indicates a range of 0.168 HP-Hr/Lb[0.276 kW-Hr/kg] to 0.182 HP-Hr/Lb [0.300 kW-Hr/kg], which is believedto be based on an on-stream factor of 340 days per year for the LNGproduction plant. On this same basis, the specific power consumption forthe FIG. 1 embodiment of the present invention is 0.161 HP-Hr/Lb [0.265kW-Hr/kg], which gives an efficiency improvement of 4-13% over the priorart processes. Further, it should be noted that the specific powerconsumption for the prior art processes is based on co-producing only anLPG (C₃ and heavier hydrocarbons) or condensate (C₄ and heavierhydrocarbons) liquid stream at relatively low recovery levels, not anNGL (C₂ and heavier hydrocarbons) liquid stream as shown for thisexample of the present invention. The prior art processes requireconsiderably more refrigeration power to co-produce an NGL streaminstead of an LPG stream or a condensate stream.

[0046] There are two primary factors that account for the improvedefficiency of the present invention. The first factor can be understoodby examining the thermodynamics of the liquefaction process when appliedto a high pressure gas stream such as that considered in this example.Since the primary constituent of this stream is methane, thethermodynamic properties of methane can be used for the purposes ofcomparing the liquefaction cycle employed in the prior art processesversus the cycle used in the present invention. FIG. 2 contains apressure-enthalpy phase diagram for methane. In most of the prior artliquefaction cycles, all cooling of the gas stream is accomplished whilethe stream is at high pressure (path A-B), whereupon the stream is thenexpanded (path B-C) to the pressure of the LNG storage vessel (slightlyabove atmospheric pressure). This expansion step may employ a workexpansion machine, which is typically capable of recovering on the orderof 75-80% of the work theoretically available in an ideal isentropicexpansion. In the interest of simplicity, fully isentropic expansion isdisplayed in FIG. 2 for path B-C. Even so, the enthalpy reductionprovided by this work expansion is quite small, because the lines ofconstant entropy are nearly vertical in the liquid region of the phasediagram.

[0047] Contrast this now with the liquefaction cycle of the presentinvention. After partial cooling at high pressure (path A-A′), the gasstream is work expanded (path A′-A″) to an intermediate pressure.(Again, fully isentropic expansion is displayed in the interest ofsimplicity.) The remainder of the cooling is accomplished at theintermediate pressure (path A″-B′), and the stream is then expanded(path B′-C) to the pressure of the LNG storage vessel. Since the linesof constant entropy slope less steeply in the vapor region of the phasediagram, a significantly larger enthalpy reduction is provided by thefirst work expansion step (path A′-A″) of the present invention. Thus,the total amount of cooling required for the present invention (the sumof paths A-A′ and A″-B′) is less than the cooling required for the priorart processes (path A-B), reducing the refrigeration (and hence therefrigeration compression) required to liquefy the gas stream.

[0048] The second factor accounting for the improved efficiency of thepresent invention is the superior performance of hydrocarbondistillation systems at lower operating pressures. The hydrocarbonremoval step in most of the prior art processes is performed at highpressure, typically using a scrub column that employs a cold hydrocarbonliquid as the absorbent stream to remove the heavier hydrocarbons fromthe incoming gas stream. Operating the scrub column at high pressure isnot very efficient, as it results in the co-absorption of a significantfraction of the methane and ethane from the gas stream, which mustsubsequently be stripped from the absorbent liquid and cooled to becomepart of the LNG product. In the present invention, the hydrocarbonremoval step is conducted at the intermediate pressure where thevapor-liquid equilibrium is much more favorable, resulting in veryefficient recovery of the desired heavier hydrocarbons in the co-productliquid stream.

EXAMPLE 2

[0049] If the specifications for the LNG product will allow more of theethane contained in the feed gas to be recovered in the LNG product, asimpler embodiment of the present invention may be employed. FIG. 3illustrates such an alternative embodiment. The inlet gas compositionand conditions considered in the process presented in FIG. 3 are thesame as those in FIG. 1. Accordingly, the FIG. 3 process can be comparedto the embodiment displayed in FIG. 1.

[0050] In the simulation of the FIG. 3 process, the inlet gas cooling,separation, and expansion scheme for the NGL recovery section isessentially the same as that used in FIG. 1. Inlet gas enters the plantat 90° F. [32° C.] and 1285 psia [8,860 kPa(a)] as stream 31 and iscooled in heat exchanger 10 by heat exchange with refrigerant streamsand demethanizer side reboiler liquids at −35° F. [−37° C.] (stream 40).The cooled stream 31 a enters separator 11 at −30° F. [−34° C.] and 1278psia [8,812 kPa(a)] where the vapor (stream 32) is separated from thecondensed liquid (stream 33).

[0051] The vapor (stream 32) from separator 11 is divided into twostreams, 34 and 36. Stream 34, containing about 20% of the total vapor,is combined with the condensed liquid, stream 33, to form stream 35.Combined stream 35 passes through heat exchanger 13 in heat exchangerelation with refrigerant stream 71 e, resulting in cooling andsubstantial condensation of stream 35 a. The substantially condensedstream 35 a at −120° F. [−85° C.] is then flash expanded through anappropriate expansion device, such as expansion valve 14, to theoperating pressure (approximately 465 psia [3,206 kPa(a)]) offractionation tower 19. During expansion a portion of the stream isvaporized, resulting in cooling of the total stream. In the processillustrated in FIG. 3, the expanded stream 35 b leaving expansion valve14 reaches a temperature of −122° F. [−86° C.], and is supplied to theseparator section in the upper region of fractionation tower 19. Theliquids separated therein become the top feed to the demethanizingsection in the lower region of fractionation tower 19.

[0052] The remaining 80% of the vapor from separator 11 (stream 36)enters a work expansion machine 15 in which mechanical energy isextracted from this portion of the high pressure feed. The machine 15expands the vapor substantially isentropically from a pressure of about1278 psia [8,812 kPa(a)] to the tower operating pressure, with the workexpansion cooling the expanded stream 36 a to a temperature ofapproximately −103° F. [−75° C.]. The expanded and partially condensedstream 36 a is supplied as feed to distillation column 19 at amid-column feed point.

[0053] The cold demethanizer overhead vapor (stream 37) exits the top offractionation tower 19 at −123° F. [−86° C.]. The liquid product stream41 exits the bottom of the tower at 118° F. [48° C.], based on a typicalspecification of a methane to ethane ratio of 0.020:1 on a molar basisin the bottom product.

[0054] The demethanizer overhead vapor (stream 37) is warmed to 90° F.[32° C.] in heat exchanger 24, and a portion (stream 48) is thenwithdrawn to serve as fuel gas for the plant. The remainder of thewarmed demethanizer overhead vapor (stream 49) is compressed bycompressor 16. After cooling to 100° F. [38° C.] in discharge cooler 25,stream 49 b is further cooled to −112° F. [−80° C.] in heat exchanger 24by cross exchange with the cold demethanizer overhead vapor, stream 37.

[0055] Stream 49 c then enters heat exchanger 60 and is further cooledby refrigerant stream 71 d to −257° F. [−160° C.] to condense andsubcool it, whereupon it enters a work expansion machine 61 in whichmechanical energy is extracted from the stream. The machine 61 expandsliquid stream 49 d substantially isentropically from a pressure of about583 psia [4,021 kPa(a)] to the LNG storage pressure (15.5 psia [107kPa(a)]), slightly above atmospheric pressure. The work expansion coolsthe expanded stream 49 e to a temperature of approximately −258° F.[−161° C.], whereupon it is then directed to the LNG storage tank 62which holds the LNG product (stream 50).

[0056] Similar to the FIG. 1 process, all of the cooling for streams 35and 49 c is provided by a closed cycle refrigeration loop. Thecomposition of the stream used as the working fluid in the cycle for theFIG. 3 process, in approximate mole percent, is 7.5% nitrogen, 40.0%methane, 42.5% ethane, and 10.0% propane, with the balance made up ofheavier hydrocarbons. The refrigerant stream 71 leaves discharge cooler69 at 100° F. [38° C.] and 607 psia [4,185 kPa(a)]. It enters heatexchanger 10 and is cooled to −31 ° F. [−35° C.] and partially condensedby the partially warmed expanded refrigerant stream 71 f and by otherrefrigerant streams. For the FIG. 3 simulation, it has been assumed thatthese other refrigerant streams are commercial-quality propanerefrigerant at three different temperature and pressure levels. Thepartially condensed refrigerant stream 71 a then enters heat exchanger13 for further cooling to −121° F. [−85° C.] by partially warmedexpanded refrigerant stream 71 e, condensing and partially subcoolingthe refrigerant (stream 71 b). The refrigerant is further subcooled to−257° F. [−160° C.] in heat exchanger 60 by expanded refrigerant stream71 d. The subcooled liquid stream 71 c enters a work expansion machine63 in which mechanical energy is extracted from the stream as it isexpanded substantially isentropically from a pressure of about 586 psia[4,040 kPa(a)] to about 34 psia [234 kPa(a)]. During expansion a portionof the stream is vaporized, resulting in cooling of the total stream to−263° F. [−164° C.] (stream 71 d). The expanded stream 71 d thenreenters heat exchangers 60, 13, and 10 where it provides cooling tostream 49 c, stream 35, and the refrigerant (streams 71, 71 a, and 71 b)as it is vaporized and superheated.

[0057] The superheated refrigerant vapor (stream 71 g) leaves heatexchanger 10 at 93° F. [34° C.] and is compressed in three stages to 617psia [4,254 kPa(a)]. Each of the three compression stages (refrigerantcompressors 64, 66, and 68) is driven by a supplemental power source andis followed by a cooler (discharge coolers 65, 67, and 69) to remove theheat of compression. The compressed stream 71 from discharge cooler 69returns to heat exchanger 10 to complete the cycle.

[0058] A summary of stream flow rates and energy consumption for theprocess illustrated in FIG. 3 is set forth in the following table: TABLEII (FIG. 3) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr] StreamMethane Ethane Propane Butanes+ Total 31 40,977 3,861 2,408 1,404 48,65632 32,360 2,675 1,469 701 37,209 33 8,617 1,186 939 703 11,447 34 6,472535 294 140 7,442 36 25,888 2,140 1,175 561 29,767 37 40,910 480 62 741,465 41 67 3,381 2,346 1,397 7,191 48 2,969 35 4 0 3,009 50 37,941 44558 7 38,456 Recoveries in NGL* Ethane 87.57% Propane 97.41% Butanes+99.47% Production Rate 296,175 Lb/Hr [296,175 kg/Hr] LNG ProductProduction Rate 625,152 Lb/Hr [625,152 kg/Hr] Purity* 98.66% LowerHeating Value  919.7 BTU/SCF [34.27 MJ/m³] Power Refrigerant Compression 96,560 HP [158,743 kW] Propane Compression  34,724 HP [57,086 kW] TotalCompression 131,284 HP [215,829 kW] Utility Heat Demethanizer Reboiler 22,177 MBTU/Hr [14,326 kW]

[0059] Assuming an on-stream factor of 340 days per year for the LNGproduction plant, the specific power consumption for the FIG. 3embodiment of the present invention is 0.153 HP-Hr/Lb [0.251 kW-Hr/kg].Compared to the prior art processes, the efficiency improvement is10-20% for the FIG. 3 embodiment. As noted earlier for the FIG. 1embodiment, this efficiency improvement is possible with the presentinvention even though an NGL co-product is produced rather than the LPGor condensate co-product produced by the prior art processes.

[0060] Compared to the FIG. 1 embodiment, the FIG. 3 embodiment of thepresent invention requires about 5% less power per unit of liquidproduced. Thus, for a given amount of available compression power, theFIG. 3 embodiment could liquefy about 5% more natural gas than the FIG.1 embodiment by virtue of recovering less of the C₂ and heavierhydrocarbons in the NGL co-product. The choice between the FIG. 1 andthe FIG. 3 embodiments of the present invention for a particularapplication will generally be dictated either by the monetary value ofthe heavier hydrocarbons in the NGL product versus their correspondingvalue in the LNG product, or by the heating value specification for theLNG product (since the heating value of the LNG produced by the FIG. 1embodiment is lower than that produced by the FIG. 3 embodiment).

EXAMPLE 3

[0061] If the specifications for the LNG product will allow all of theethane contained in the feed gas to be recovered in the LNG product, orif there is no market for a liquid co-product containing ethane, analternative embodiment of the present invention such as that shown inFIG. 4 may be employed to produce an LPG co-product stream. The inletgas composition and conditions considered in the process presented inFIG. 4 are the same as those in FIGS. 1 and 3. Accordingly, the FIG. 4process can be compared to the embodiments displayed in FIGS. 1 and 3.

[0062] In the simulation of the FIG. 4 process, inlet gas enters theplant at 90° F. [32° C.] and 1285 psia [8,860 kPa(a)] as stream 31 andis cooled in heat exchanger 10 by heat exchange with refrigerant streamsand flashed separator liquids at −46° F. [−43° C.] (stream 33 a). Thecooled stream 31 a enters separator 11 at −1° F. [−18° C.] and 1278 psia[8,812 kPa(a)] where the vapor (stream 32) is separated from thecondensed liquid (stream 33).

[0063] The vapor (stream 32) from separator 11 enters work expansionmachine 15 in which mechanical energy is extracted from this portion ofthe high pressure feed. The machine 15 expands the vapor substantiallyisentropically from a pressure of about 1278 psia [8,812 kPa(a)] to apressure of about 440 psia [3,034 kPa(a)] (the operating pressure ofseparator/absorber tower 18), with the work expansion cooling theexpanded stream 32 a to a temperature of approximately −81° F. [−63°C.]. The expanded and partially condensed stream 32 a is supplied toabsorbing section 18 b in a lower region of separator/absorber tower 18.The liquid portion of the expanded stream commingles with liquidsfalling downward from the absorbing section and the combined liquidstream 40 exits the bottom of separator/absorber tower 18 at −86° F.[−66° C.]. The vapor portion of the expanded stream rises upward throughthe absorbing section and is contacted with cold liquid falling downwardto condense and absorb the C₃ components and heavier components.

[0064] The separator/absorber tower 18 is a conventional distillationcolumn containing a plurality of vertically spaced trays, one or morepacked beds, or some combination of trays and packing. As is often thecase in natural gas processing plants, the separator/absorber tower mayconsist of two sections. The upper section 18 a is a separator whereinany vapor contained in the top feed is separated from its correspondingliquid portion, and wherein the vapor rising from the lower distillationor absorbing section 18 b is combined with the vapor portion (if any) ofthe top feed to form the cold distillation stream 37 which exits the topof the tower. The lower, absorbing section 18 b contains the traysand/or packing and provides the necessary contact between the liquidsfalling downward and the vapors rising upward to condense and absorb theC₃ components and heavier components.

[0065] The combined liquid stream 40 from the bottom ofseparator/absorber tower 18 is routed to heat exchanger 13 by pump 26where it (stream 40 a) is heated as it provides cooling of deethanizeroverhead (stream 42) and refrigerant (stream 71 a). The combined liquidstream is heated to −24° F. [−31° C.], partially vaporizing stream 40 bbefore it is supplied as a mid-column feed to deethanizer 19. Theseparator liquid (stream 33) is flash expanded to slightly above theoperating pressure of deethanizer 19 by expansion valve 12, coolingstream 33 to −46° F. [−43° C.] (stream 33 a) before it provides coolingto the incoming feed gas as described earlier. Stream 33 b, now at 85°F. [29° C.], then enters deethanizer 19 at a lower mid-column feedpoint. In the deethanizer, streams 40 b and 33 b are stripped of theirmethane and C₂ components. The deethanizer in tower 19, operating atabout 453 psia [3,123 kPa(a)], is also a conventional distillationcolumn containing a plurality of vertically spaced trays, one or morepacked beds, or some combination of trays and packing. The deethanizertower may also consist of two sections: an upper separator section 19 awherein any vapor contained in the top feed is separated from itscorresponding liquid portion, and wherein the vapor rising from thelower distillation or deethanizing section 19 b is combined with thevapor portion (if any) of the top feed to form distillation stream 42which exits the top of the tower; and a lower, deethanizing section 19 bthat contains the trays and/or packing to provide the necessary contactbetween the liquids falling downward and the vapors rising upward. Thedeethanizing section 19 b also includes one or more reboilers (such asreboiler 20) which heat and vaporize a portion of the liquid at thebottom of the column to provide the stripping vapors which flow up thecolumn to strip the liquid product, stream 41, of methane and C₂components. A typical specification for the bottom liquid product is tohave an ethane to propane ratio of 0.020:1 on a molar basis. The liquidproduct stream 41 exits the bottom of the deethanizer at 214° F. [101°C.].

[0066] The operating pressure in deethanizer 19 is maintained slightlyabove the operating pressure of separator/absorber tower 18. This allowsthe deethanizer overhead vapor (stream 42) to pressure flow through heatexchanger 13 and thence into the upper section of separator/absorbertower 18. In heat exchanger 13, the deethanizer overhead at −19° F.[−28° C.] is directed in heat exchange relation with the combined liquidstream (stream 40 a) from the bottom of separator/absorber tower 18 andflashed refrigerant stream 71 e, cooling the stream to −89° F. [−67° C.](stream 42 a) and partially condensing it. The partially condensedstream enters reflux drum 22 where the condensed liquid (stream 44) isseparated from the uncondensed vapor (stream 43). Stream 43 combineswith the distillation vapor stream (stream 37) leaving the upper regionof separator/absorber tower 18 to form cold residue gas stream 47. Thecondensed liquid (stream 44) is pumped to higher pressure by pump 23,whereupon stream 44 a is divided into two portions. One portion, stream45, is routed to the upper separator section of separator/absorber tower18 to serve as the cold liquid that contacts the vapors rising upwardthrough the absorbing section. The other portion is supplied todeethanizer 19 as reflux stream 46, flowing to a top feed point ondeethanizer 19 at −89° F. [−67° C.].

[0067] The cold residue gas (stream 47) is warmed from −94° F. [−70° C.]to 94° F. [34° C.] in heat exchanger 24, and a portion (stream 48) isthen withdrawn to serve as fuel gas for the plant. The remainder of thewarmed residue gas (stream 49) is compressed by compressor 16. Aftercooling to 100° F. [38° C.] in discharge cooler 25, stream 49 b isfurther cooled to −78° F. [−61° C.] in heat exchanger 24 by crossexchange with the cold residue gas, stream 47.

[0068] Stream 49 c then enters heat exchanger 60 and is further cooledby refrigerant stream 71 d to −255° F. [−160° C.] to condense andsubcool it, whereupon it enters a work expansion machine 61 in whichmechanical energy is extracted from the stream. The machine 61 expandsliquid stream 49 d substantially isentropically from a pressure of about648 psia [4,465 kPa(a)] to the LNG storage pressure (15.5 psia [107kPa(a)]), slightly above atmospheric pressure. The work expansion coolsthe expanded stream 49 e to a temperature of approximately −256° F.[−160° C.], whereupon it is then directed to the LNG storage tank 62which holds the LNG product (stream 50).

[0069] Similar to the FIG. 1 and FIG. 3 processes, much of the coolingfor stream 42 and all of the cooling for stream 49 c is provided by aclosed cycle refrigeration loop. The composition of the stream used asthe working fluid in the cycle for the FIG. 4 process, in approximatemole percent, is 8.7% nitrogen, 30.0% methane, 45.8% ethane, and 11.0%propane, with the balance made up of heavier hydrocarbons. Therefrigerant stream 71 leaves discharge cooler 69 at 100° F. [38° C.] and607 psia [4,185 kPa(a)]. It enters heat exchanger 10 and is cooled to−17° F. [−27° C.] and partially condensed by the partially warmedexpanded refrigerant stream 71 f and by other refrigerant streams. Forthe FIG. 4 simulation, it has been assumed that these other refrigerantstreams are commercial-quality propane refrigerant at three differenttemperature and pressure levels. The partially condensed refrigerantstream 71 a then enters heat exchanger 13 for further cooling to −89° F.[−67° C.] by partially warmed expanded refrigerant stream 71 e, furthercondensing the refrigerant (stream 71 b). The refrigerant is totallycondensed and then subcooled to −255° F. [−160° C.] in heat exchanger 60by expanded refrigerant stream 71 d. The subcooled liquid stream 71 centers a work expansion machine 63 in which mechanical energy isextracted from the stream as it is expanded substantially isentropicallyfrom a pressure of about 586 psia [4,040 kPa(a)] to about 34 psia [234kPa(a)]. During expansion a portion of the stream is vaporized,resulting in cooling of the total stream to −264° F. [−164° C.] (stream71 d). The expanded stream 71 d then reenters heat exchangers 60, 13,and 10 where it provides cooling to stream 49 c, stream 42, and therefrigerant (streams 71, 71 a, and 71 b) as it is vaporized andsuperheated.

[0070] The superheated refrigerant vapor (stream 71 g) leaves heatexchanger 10 at 90° F. [32° C.] and is compressed in three stages to 617psia [4,254 kPa(a)]. Each of the three compression stages (refrigerantcompressors 64, 66, and 68) is driven by a supplemental power source andis followed by a cooler (discharge coolers 65, 67, and 69) to remove theheat of compression. The compressed stream 71 from discharge cooler 69returns to heat exchanger 10 to complete the cycle.

[0071] A summary of stream flow rates and energy consumption for theprocess illustrated in FIG. 4 is set forth in the following table: TABLEIII (FIG. 4) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr] StreamMethane Ethane Propane Butanes+ Total 31 40,977 3,861 2,408 1,404 48,65632 38,431 3,317 1,832 820 44,405 33 2,546 544 576 584 4,251 37 36,6923,350 19 0 40,066 40 5,324 3,386 1,910 820 11,440 41 0 48 2,386 1,4043,837 42 10,361 6,258 168 0 16,789 43 4,285 463 3 0 4,753 44 6,076 5,795165 0 12,036 45 3,585 3,419 97 0 7,101 46 2,491 2,376 68 0 4,935 4740,977 3,813 22 0 44,819 48 2,453 228 1 0 2,684 50 38,524 3,585 21 042,135 Recoveries in LPG* Propane  99.08% Butanes+ 100.00% ProductionRate 197,051 Lb/Hr [197,051 kg/Hr] LNG Product Production Rate 726,918Lb/Hr [726,918 kg/Hr] Purity*  91.43% Lower Heating Value  969.9 BTU/SCF[36.14 MJ/m³] Power Refrigerant Compression  95,424 HP [156,876 kW]Propane Compression  28,060 HP [46,130 kW] Total Compression 123,484 HP[203,006 kW] Utility Heat Demethanizer Reboiler  55,070 MBTU/Hr [35,575kW]

[0072] Assuming an on-stream factor of 340 days per year for the LNGproduction plant, the specific power consumption for the FIG. 4embodiment of the present invention is 0.143 HP-Hr/Lb [0.236 kW-Hr/kg].Compared to the prior art processes, the efficiency improvement is17-27% for the FIG. 4 embodiment.

[0073] Compared to the FIG. 1 and FIG. 3 embodiments, the FIG. 4embodiment of the present invention requires 6% to 11% less power perunit of liquid produced. Thus, for a given amount of availablecompression power, the FIG. 4 embodiment could liquefy about 6% morenatural gas than the FIG. 1 embodiment or about 11% more natural gasthan the FIG. 3 embodiment by virtue of recovering only the C₃ andheavier hydrocarbons as an LPG co-product. The choice between the FIG. 4embodiment versus either the FIG. 1 or FIG. 3 embodiments of the presentinvention for a particular application will generally be dictated eitherby the monetary value of ethane as part of an NGL product versus itscorresponding value in the LNG product, or by the heating valuespecification for the LNG product (since the heating value of the LNGproduced by the FIG. 1 and FIG. 3 embodiments is lower than thatproduced by the FIG. 4 embodiment).

EXAMPLE 4

[0074] If the specifications for the LNG product will allow all of theethane and propane contained in the feed gas to be recovered in the LNGproduct, or if there is no market for a liquid co-product containingethane and propane, an alternative embodiment of the present inventionsuch as that shown in FIG. 5 may be employed to produce a condensateco-product stream. The inlet gas composition and conditions consideredin the process presented in FIG. 5 are the same as those in FIGS. 1, 3,and 4. Accordingly, the FIG. 5 process can be compared to theembodiments displayed in FIGS. 1, 3, and 4.

[0075] In the simulation of the FIG. 5 process, inlet gas enters theplant at 90° F. [32° C.] and 1285 psia [8,860 kPa(a)] as stream 31 andis cooled in heat exchanger 10 by heat exchange with refrigerantstreams, flashed high pressure separator liquids at −37° F. [−38° C.](stream 33 b), and flashed intermediate pressure separator liquids at−37° F. [−38° C.] (stream 39 b). The cooled stream 31 a enters highpressure separator 11 at −30° F. [−34° C.] and 1278 psia [8,812 kPa(a)]where the vapor (stream 32) is separated from the condensed liquid(stream 33).

[0076] The vapor (stream 32) from high pressure separator 11 enters workexpansion machine 15 in which mechanical energy is extracted from thisportion of the high pressure feed. The machine 15 expands the vaporsubstantially isentropically from a pressure of about 1278 psia [8,812kPa(a)] to a pressure of about 635 psia [4,378 kPa(a)], with the workexpansion cooling the expanded stream 32 a to a temperature ofapproximately −83° F. [−64° C.]. The expanded and partially condensedstream 32 a enters intermediate pressure separator 18 where the vapor(stream 42) is separated from the condensed liquid (stream 39). Theintermediate pressure separator liquid (stream 39) is flash expanded toslightly above the operating pressure of depropanizer 19 by expansionvalve 17, cooling stream 39 to −108 F [−78° C.] (stream 39 a) before itenters heat exchanger 13 and is heated as it provides cooling to residuegas stream 49 and refrigerant stream 71 a, and thence to heat exchanger10 to provide cooling to the incoming feed gas as described earlier.Stream 39 c, now at −15° F. [−26° C.], then enters depropanizer 19 at anupper mid-column feed point.

[0077] The condensed liquid, stream 33, from high pressure separator 11is flash expanded to slightly above the operating pressure ofdepropanizer 19 by expansion valve 12, cooling stream 33 to −93 F [−70°C.] (stream 33 a) before it enters heat exchanger 13 and is heated as itprovides cooling to residue gas stream 49 and refrigerant stream 71 a,and thence to heat exchanger 10 to provide cooling to the incoming feedgas as described earlier. Stream 33 c, now at 50° F. [10° C.], thenenters depropanizer 19 at a lower mid-column feed point. In thedepropanizer, streams 39 c and 33 c are stripped of their methane, C₂components, and C₃ components. The depropanizer in tower 19, operatingat about 385 psia [2,654 kPa(a)], is a conventional distillation columncontaining a plurality of vertically spaced trays, one or more packedbeds, or some combination of trays and packing. The depropanizer towermay consist of two sections: an upper separator section 19 a wherein anyvapor contained in the top feed is separated from its correspondingliquid portion, and wherein the vapor rising from the lower distillationor depropanizing section 19 b is combined with the vapor portion (ifany) of the top feed to form distillation stream 37 which exits the topof the tower; and a lower, depropanizing section 19 b that contains thetrays and/or packing to provide the necessary contact between theliquids falling downward and the vapors rising upward. The depropanizingsection 19 b also includes one or more reboilers (such as reboiler 20)which heat and vaporize a portion of the liquid at the bottom of thecolumn to provide the stripping vapors which flow up the column to stripthe liquid product, stream 41, of methane, C₂ components, and C₃components. A typical specification for the bottom liquid product is tohave a propane to butanes ratio of 0.020:1 on a volume basis. The liquidproduct stream 41 exits the bottom of the deethanizer at 286° F. [141°C.].

[0078] The overhead distillation stream 37 leaves depropanizer 19 at 36°F. [2° C.] and is cooled and partially condensed by commercial-qualitypropane refrigerant in reflux condenser 21. The partially condensedstream 37 a enters reflux drum 22 at 2° F. [−17° C.] where the condensedliquid (stream 44) is separated from the uncondensed vapor (stream 43).The condensed liquid (stream 44) is pumped by pump 23 to a top feedpoint on depropanizer 19 as reflux stream 44 a.

[0079] The uncondensed vapor (stream 43) from reflux drum 22 is warmedto 94° F. [34° C.] in heat exchanger 24, and a portion (stream 48) isthen withdrawn to serve as fuel gas for the plant. The remainder of thewarmed vapor (stream 38) is compressed by compressor 16. After coolingto 100° F. [38° C.] in discharge cooler 25, stream 38 b is furthercooled to 15° F. [−9° C.] in heat exchanger 24 by cross exchange withthe cool vapor, stream 43.

[0080] Stream 38 c then combines with the intermediate pressureseparator vapor (stream 42) to form cool residue gas stream 49. Stream49 enters heat exchanger 13 and is cooled from −38° F. [−39° C.] to−102° F. [−74° C.] by separator liquids (streams 39 a and 33 a) asdescribed earlier and by refrigerant stream 71 e. Partially condensedstream 49 a then enters heat exchanger 60 and is further cooled byrefrigerant stream 71 d to −254° F. [−159° C.] to condense and subcoolit, whereupon it enters a work expansion machine 61 in which mechanicalenergy is extracted from the stream. The machine 61 expands liquidstream 49 b substantially isentropically from a pressure of about 621psia [4,282 kPa(a)] to the LNG storage pressure (15.5 psia [107kPa(a)]), slightly above atmospheric pressure. The work expansion coolsthe expanded stream 49 c to a temperature of approximately −255° F.[−159° C.], whereupon it is then directed to the LNG storage tank 62which holds the LNG product (stream 50).

[0081] Similar to the FIG. 1, FIG. 3, and FIG. 4 processes, much of thecooling for stream 49 and all of the cooling for stream 49 a is providedby a closed cycle refrigeration loop. The composition of the stream usedas the working fluid in the cycle for the FIG. 5 process, in approximatemole percent, is 8.9% nitrogen, 34.3% methane, 41.3% ethane, and 11.0%propane, with the balance made up of heavier hydrocarbons. Therefrigerant stream 71 leaves discharge cooler 69 at 100° F. [38° C.] and607 psia [4,185 kPa(a)]. It enters heat exchanger 10 and is cooled to−30° F. [−34° C.] and partially condensed by the partially warmedexpanded refrigerant stream 71 f and by other refrigerant streams. Forthe FIG. 5 simulation, it has been assumed that these other refrigerantstreams are commercial-quality propane refrigerant at three differenttemperature and pressure levels. The partially condensed refrigerantstream 71 a then enters heat exchanger 13 for further cooling to −102°F. [−74° C.] by partially warmed expanded refrigerant stream 71 e,further condensing the refrigerant (stream 71 b). The refrigerant istotally condensed and then subcooled to −254° F. [−159° C.] in heatexchanger 60 by expanded refrigerant stream 71 d. The subcooled liquidstream 71 c enters a work expansion machine 63 in which mechanicalenergy is extracted from the stream as it is expanded substantiallyisentropically from a pressure of about 586 psia [4,040 kPa(a)] to about34 psia [234 kPa(a)]. During expansion a portion of the stream isvaporized, resulting in cooling of the total stream to −264° F. [−164°C.] (stream 71 d). The expanded stream 71 d then reenters heatexchangers 60, 13, and 10 where it provides cooling to stream 49 a,stream 49, and the refrigerant (streams 71, 71 a, and 71 b) as it isvaporized and superheated.

[0082] The superheated refrigerant vapor (stream 71 g) leaves heatexchanger 10 at 93° F. [34° C.] and is compressed in three stages to 617psia [4,254 kPa(a)]. Each of the three compression stages (refrigerantcompressors 64, 66, and 68) is driven by a supplemental power source andis followed by a cooler (discharge coolers 65, 67, and 69) to remove theheat of compression. The compressed stream 71 from discharge cooler 69returns to heat exchanger 10 to complete the cycle.

[0083] A summary of stream flow rates and energy consumption for theprocess illustrated in FIG. 5 is set forth in the following table: TABLEIV (FIG. 5) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr] StreamMethane Ethane Propane Butanes+ Total 31 40,977 3,861 2,408 1,404 48,65632 32,360 2,675 1,469 701 37,209 33 8,617 1,186 939 703 11,447 38 13,1332,513 1,941 22 17,610 39 6,194 1,648 1,272 674 9,788 41 0 0 22 1,3521,375 42 26,166 1,027 197 27 27,421 43 14,811 2,834 2,189 25 19,860 481,678 321 248 3 2,250 50 39,299 3,540 2,138 49 45,031 Recoveries inCondensate* Butanes 95.04% Pentanes+ 99.57% Production Rate  88,390Lb/Hr [88,390 kg/Hr] LNG Product Production Rate 834,183 Lb/Hr [834,183kg/Hr] Purity* 87.27% Lower Heating Value  1033.8 BTU/SCF [38.52 MJ/m³]Power Refrigerant Compression  84,974 HP [139,696 kW] PropaneCompression  39,439 HP [64,837 kW] Total Compression 124,413 HP [204,533kW] Utility Heat Demethanizer Reboiler  52,913 MBTU/Hr [34,182 kW]

[0084] Assuming an on-stream factor of 340 days per year for the LNGproduction plant, the specific power consumption for the FIG. 5embodiment of the present invention is 0.145 HP-Hr/Lb [0.238 kW-Hr/kg].Compared to the prior art processes, the efficiency improvement is16-26% for the FIG. 5 embodiment.

[0085] Compared to the FIG. 1 and FIG. 3 embodiments, the FIG. 5embodiment of the present invention requires 5% to 10% less power perunit of liquid produced. Compared to the FIG. 4 embodiment, the FIG. 5embodiment of the present invention requires essentially the same powerper unit of liquid produced. Thus, for a given amount of availablecompression power, the FIG. 5 embodiment could liquefy about 5% morenatural gas than the FIG. 1 embodiment, about 10% more natural gas thanthe FIG. 3 embodiment, or about the same amount of natural gas as theFIG. 4 embodiment, by virtue of recovering only the C₄ and heavierhydrocarbons as a condensate co-product. The choice between the FIG. 5embodiment versus either the FIG. 1, FIG. 3, or FIG. 4 embodiments ofthe present invention for a particular application will generally bedictated either by the monetary values of ethane and propane as part ofan NGL or LPG product versus their corresponding values in the LNGproduct, or by the heating value specification for the LNG product(since the heating value of the LNG produced by the FIG. 1, FIG. 3, andFIG. 4 embodiments is lower than that produced by the FIG. 5embodiment).

Other Embodiments

[0086] One skilled in the art will recognize that the present inventioncan be adapted for use with all types of LNG liquefaction plants toallow co-production of an NGL stream, an LPG stream, or a condensatestream, as best suits the needs at a given plant location. Further, itwill be recognized that a variety of process configurations may beemployed for recovering the liquid co-product stream. For instance, theFIGS. 1 and 3 embodiments can be adapted to recover an LPG stream or acondensate stream as the liquid co-product stream rather than an NGLstream as described earlier in Examples 1 and 2. The FIG. 4 embodimentcan be adapted to recover an NGL stream containing a significantfraction of the C₂ components present in the feed gas, or to recover acondensate stream containing only the C₄ and heavier components presentin the feed gas, rather than producing an LPG co-product as describedearlier for Example 3. The FIG. 5 embodiment can be adapted to recoveran NGL stream containing a significant fraction of the C₂ componentspresent in the feed gas, or to recover an LPG stream containing asignificant fraction of the C₃ components present in the feed gas,rather than producing a condensate co-product as described earlier forExample 4.

[0087]FIGS. 1, 3, 4, and 5 represent the preferred embodiments of thepresent invention for the processing conditions indicated. FIGS. 6through 21 depict alternative embodiments of the present invention thatmay be considered for a particular application. As shown in FIGS. 6 and7, all or a portion of the condensed liquid (stream 33) from separator11 can be supplied to fractionation tower 19 at a separate lowermid-column feed position rather than combining with the portion of theseparator vapor (stream 34) flowing to heat exchanger 13. FIG. 8 depictsan alternative embodiment of the present invention that requires lessequipment than the FIG. 1 and FIG. 6 embodiments, although its specificpower consumption is somewhat higher. Similarly, FIG. 9 depicts analternative embodiment of the present invention that requires lessequipment than the FIG. 3 and FIG. 7 embodiments, again at the expenseof a higher specific power consumption. FIGS. 10 through 14 depictalternative embodiments of the present invention that may require lessequipment than the FIG. 4 embodiment, although their specific powerconsumptions may be higher. (Note that as shown in FIGS. 10 through 14,distillation columns or systems such as deethanizer 19 include bothreboiled absorber tower designs and refluxed, reboiled tower designs.)FIGS. 15 and 16 depict alternative embodiments of the present inventionthat combine the functions of separator/absorber tower 18 anddeethanizer 19 in the FIGS. 4 and 10 through 14 embodiments into asingle fractionation column 19. Depending on the quantity of heavierhydrocarbons in the feed gas and the feed gas pressure, the cooled feedstream 31 a leaving heat exchanger 10 may not contain any liquid(because it is above its dewpoint, or because it is above itscricondenbar), so that separator 11 shown in FIGS. 1 and 3 through 16 isnot required, and the cooled feed stream can flow directly to anappropriate expansion device, such as work expansion machine 15.

[0088] The disposition of the gas stream remaining after recovery of theliquid co-product stream (stream 37 in FIGS. 1, 3, 6 through 11, 13, and14, stream 47 in FIGS. 4, 12, 15, and 16, and stream 43 in FIG. 5)before it is supplied to heat exchanger 60 for condensing and subcoolingmay be accomplished in many ways. In the processes of FIGS. 1 and 3through 16, the stream is heated, compressed to higher pressure usingenergy derived from one or more work expansion machines, partiallycooled in a discharge cooler, then further cooled by cross exchange withthe original stream. As shown in FIG. 17, some applications may favorcompressing the stream to higher pressure, using supplemental compressor59 driven by an external power source for example. As shown by thedashed equipment (heat exchanger 24 and discharge cooler 25) in FIGS. 1and 3 through 16, some circumstances may favor reducing the capital costof the facility by reducing or eliminating the pre-cooling of thecompressed stream before it enters heat exchanger 60 (at the expense ofincreasing the cooling load on heat exchanger 60 and increasing thepower consumption of refrigerant compressors 64, 66, and 68). In suchcases, stream 49 a leaving the compressor may flow directly to heatexchanger 24 as shown in FIG. 18, or flow directly to heat exchanger 60as shown in FIG. 19. If work expansion machines are not used forexpansion of any portions of the high pressure feed gas, a compressordriven by an external power source, such as compressor 59 shown in FIG.20, may be used in lieu of compressor 16. Other circumstances may notjustify any compression of the stream at all, so that the stream flowsdirectly to heat exchanger 60 as shown in FIG. 21 and by the dashedequipment (heat exchanger 24, compressor 16, and discharge cooler 25) inFIGS. 1 and 3 through 16. If heat exchanger 24 is not included to heatthe stream before the plant fuel gas (stream 48) is withdrawn, asupplemental heater 58 may be needed to warm the fuel gas before it isconsumed, using a utility stream or another process stream to supply thenecessary heat, as shown in FIGS. 19 through 21. Choices such as thesemust generally be evaluated for each application, as factors such as gascomposition, plant size, desired co-product stream recovery level, andavailable equipment must all be considered.

[0089] In accordance with the present invention, the cooling of theinlet gas stream and the feed stream to the LNG production section maybe accomplished in many ways. In the processes of FIGS. 1, 3, and 6through 9, inlet gas stream 31 is cooled and condensed by externalrefrigerant streams and tower liquids from fractionation tower 19. InFIGS. 4, 5, and 10 through 14 flashed separator liquids are used forthis purpose along with the external refrigerant streams. In FIGS. 15and 16 tower liquids and flashed separator liquids are used for thispurpose along with the external refrigerant streams. And in FIGS. 17through 21, only external refrigerant streams are used to cool inlet gasstream 31. However, the cold process streams could also be used tosupply some of the cooling to the high pressure refrigerant (stream 71a), such as shown in FIGS. 4, 5, 10, and 11. Further, any stream at atemperature colder than the stream(s) being cooled may be utilized. Forinstance, a side draw of vapor from separator/absorber tower 18 orfractionation tower 19 could be withdrawn and used for cooling. The useand distribution of tower liquids and/or vapors for process heatexchange, and the particular arrangement of heat exchangers for inletgas and feed gas cooling, must be evaluated for each particularapplication, as well as the choice of process streams for specific heatexchange services. The selection of a source of cooling will depend on anumber of factors including, but not limited to, feed gas compositionand conditions, plant size, heat exchanger size, potential coolingsource temperature, etc. One skilled in the art will also recognize thatany combination of the above cooling sources or methods of cooling maybe employed in combination to achieve the desired feed streamtemperature(s).

[0090] Further, the supplemental external refrigeration that is suppliedto the inlet gas stream and the feed stream to the LNG productionsection may also be accomplished in many different ways. In FIGS. 1 and3 through 21, boiling single-component refrigerant has been assumed forthe high level external refrigeration and vaporizing multi-componentrefrigerant has been assumed for the low level external refrigeration,with the single-component refrigerant used to pre-cool themulti-component refrigerant stream. Alternatively, both the high levelcooling and the low level cooling could be accomplished usingsingle-component refrigerants with successively lower boiling points(i.e., “cascade refrigeration”), or one single-component refrigerant atsuccessively lower evaporation pressures. As another alternative, boththe high level cooling and the low level cooling could be accomplishedusing multi-component refrigerant streams with their respectivecompositions adjusted to provide the necessary cooling temperatures. Theselection of the method for providing external refrigeration will dependon a number of factors including, but not limited to, feed gascomposition and conditions, plant size, compressor driver size, heatexchanger size, ambient heat sink temperature, etc. One skilled in theart will also recognize that any combination of the methods forproviding external refrigeration described above may be employed incombination to achieve the desired feed stream temperature(s).

[0091] Subcooling of the condensed liquid stream leaving heat exchanger60 (stream 49 in FIGS. 1, 6, and 8, stream 49 d in FIGS. 3, 4, 7, and 9through 16, stream 49 b in FIGS. 5, 19, and 20, stream 49 e in FIG. 17,stream 49 c in FIG. 18, and stream 49 a in FIG. 21) reduces oreliminates the quantity of flash vapor that may be generated duringexpansion of the stream to the operating pressure of LNG storage tank62. This generally reduces the specific power consumption for producingthe LNG by eliminating the need for flash gas compression. However, somecircumstances may favor reducing the capital cost of the facility byreducing the size of heat exchanger 60 and using flash gas compressionor other means to dispose of any flash gas that may be generated.

[0092] Although individual stream expansion is depicted in particularexpansion devices, alternative expansion means may be employed whereappropriate. For example, conditions may warrant work expansion of thesubstantially condensed feed stream (stream 35 a in FIGS. 1, 3, 6, and7) or the intermediate pressure reflux stream (stream 39 in FIGS. 1, 6,and 8). Further, isenthalpic flash expansion may be used in lieu of workexpansion for the subcooled liquid stream leaving heat exchanger 60(stream 49 in FIGS. 1, 6, and 8, stream 49 d in FIGS. 3, 4, 7, and 9through 16, stream 49 b in FIGS. 5, 19, and 20, stream 49 e in FIG. 17,stream 49 c in FIG. 18, and stream 49 a in FIG. 21), but willnecessitate either more subcooling in heat exchanger 60 to avoid formingflash vapor in the expansion, or else adding flash vapor compression orother means for disposing of the flash vapor that results. Similarly,isenthalpic flash expansion may be used in lieu of work expansion forthe subcooled high pressure refrigerant stream leaving heat exchanger 60(stream 71 c in FIGS. 1 and 3 through 21), with the resultant increasein the power consumption for compression of the refrigerant.

[0093] While there have been described what are believed to be preferredembodiments of the invention, those skilled in the art will recognizethat other and further modifications may be made thereto, e.g. to adaptthe invention to various conditions, types of feed, or otherrequirements without departing from the spirit of the present inventionas defined by the following claims.

We claim:
 1. In a process for liquefying a natural gas stream containingmethane and heavier hydrocarbon components wherein (a) said natural gasstream is cooled under pressure to condense at least a portion of it andform a condensed stream; and (b) said condensed stream is expanded tolower pressure to form said liquefied natural gas stream; theimprovement wherein (1) said natural gas stream is treated in one ormore cooling steps; (2) said cooled natural gas stream is expanded to anintermediate pressure; (3) said expanded cooled natural gas stream isdirected into a distillation column wherein said stream is separatedinto a volatile residue gas fraction containing a major portion of saidmethane and lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (4)said volatile residue gas fraction is cooled under pressure to condenseat least a portion of it; (5) said condensed portion is divided into atleast two portions to form thereby said condensed stream and a liquidstream; and (6) said liquid stream is directed into said distillationcolumn as a top feed thereto.
 2. In a process for liquefying a naturalgas stream containing methane and heavier hydrocarbon components wherein(a) said natural gas stream is cooled under pressure to condense atleast a portion of it and form a condensed stream; and (b) saidcondensed stream is expanded to lower pressure to form said liquefiednatural gas stream; the improvement wherein (1) said natural gas streamis treated in one or more cooling steps to partially condense it; (2)said partially condensed natural gas stream is separated to providethereby at least a vapor stream and a first liquid stream; (3) saidvapor stream is expanded to an intermediate pressure; (4) said firstliquid stream is expanded to said intermediate pressure; (5) at leastsaid expanded vapor stream and said expanded first liquid stream aredirected into a distillation column wherein said streams are separatedinto a volatile residue gas fraction containing a major portion of saidmethane and lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (6)said volatile residue gas fraction is cooled under pressure to condenseat least a portion of it; (7) said condensed portion is divided into atleast two portions to form thereby said condensed stream and a secondliquid stream; and (8) said second liquid stream is directed into saiddistillation column as a top feed thereto.
 3. In a process forliquefying a natural gas stream containing methane and heavierhydrocarbon components wherein (a) said natural gas stream is cooledunder pressure to condense at least a portion of it and form a condensedstream; and (b) said condensed stream is expanded to lower pressure toform said liquefied natural gas stream; the improvement wherein (1) saidnatural gas stream is treated in one or more cooling steps; (2) saidcooled natural gas stream is divided into at least a first gaseousstream and a second gaseous stream; (3) said first gaseous stream iscooled to condense substantially all of it and thereafter expanded to anintermediate pressure; (4) said second gaseous stream is expanded tosaid intermediate pressure; (5) said expanded substantially condensedgaseous first stream and said expanded gaseous second stream aredirected into a distillation column wherein said streams are separatedinto a volatile residue gas fraction containing a major portion of saidmethane and lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; and(6) said volatile residue gas fraction is cooled under pressure tocondense at least a portion of it and form thereby said condensedstream.
 4. In a process for liquefying a natural gas stream containingmethane and heavier hydrocarbon components wherein (a) said natural gasstream is cooled under pressure to condense at least a portion of it andform a condensed stream; and (b) said condensed stream is expanded tolower pressure to form said liquefied natural gas stream; theimprovement wherein (1) said natural gas stream is treated in one ormore cooling steps to partially condense it; (2) said partiallycondensed natural gas stream is separated to provide thereby a vaporstream and a liquid stream; (3) said vapor stream is divided into atleast a first gaseous stream and a second gaseous stream; (4) said firstgaseous stream is cooled to condense substantially all of it andthereafter expanded to an intermediate pressure; (5) said second gaseousstream is expanded to said intermediate pressure; (6) said liquid streamis expanded to said intermediate pressure; (7) said expandedsubstantially condensed gaseous first stream, said expanded gaseoussecond stream, and said expanded liquid stream are directed into adistillation column wherein said streams are separated into a volatileresidue gas fraction containing a major portion of said methane andlighter components and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; and (8) saidvolatile residue gas fraction is cooled under pressure to condense atleast a portion of it and form thereby said condensed stream.
 5. In aprocess for liquefying a natural gas stream containing methane andheavier hydrocarbon components wherein (a) said natural gas stream iscooled under pressure to condense at least a portion of it and form acondensed stream; and (b) said condensed stream is expanded to lowerpressure to form said liquefied natural gas stream; the improvementwherein (1) said natural gas stream is treated in one or more coolingsteps to partially condense it; (2) said partially condensed natural gasstream is separated to provide thereby a vapor stream and a liquidstream; (3) said vapor stream is divided into at least a first gaseousstream and a second gaseous stream; (4) said first gaseous stream iscombined with at least a portion of said liquid stream, forming therebya combined stream; (5) said combined stream is cooled to condensesubstantially all of it and thereafter expanded to an intermediatepressure; (6) said second gaseous stream is expanded to saidintermediate pressure; (7) any remaining portion of said liquid streamis expanded to said intermediate pressure; (8) said expandedsubstantially condensed combined stream, said expanded gaseous secondstream, and said remaining portion of said liquid stream are directedinto a distillation column wherein said streams are separated into avolatile residue gas fraction containing a major portion of said methaneand lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; and(9) said volatile residue gas fraction is cooled under pressure tocondense at least a portion of it and form thereby said condensedstream.
 6. In a process for liquefying a natural gas stream containingmethane and heavier hydrocarbon components wherein (a) said natural gasstream is cooled under pressure to condense at least a portion of it andform a condensed stream; and (b) said condensed stream is expanded tolower pressure to form said liquefied natural gas stream; theimprovement wherein (1) said natural gas stream is treated in one ormore cooling steps; (2) said cooled natural gas stream is divided intoat least a first gaseous stream and a second gaseous stream; (3) saidfirst gaseous stream is cooled to condense substantially all of it andthereafter expanded to an intermediate pressure; (4) said second gaseousstream is expanded to said intermediate pressure; (5) said expandedsubstantially condensed gaseous first stream and said expanded gaseoussecond stream are directed into a distillation column wherein saidstreams are separated into a volatile residue gas fraction containing amajor portion of said methane and lighter components and a relativelyless volatile fraction containing a major portion of said heavierhydrocarbon components; (6) said volatile residue gas fraction is cooledunder pressure to condense at least a portion of it; (7) said condensedportion is divided into at least two portions to form thereby saidcondensed stream and a liquid stream; and (8) said liquid stream isdirected into said distillation column as a top feed thereto.
 7. In aprocess for liquefying a natural gas stream containing methane andheavier hydrocarbon components wherein (a) said natural gas stream iscooled under pressure to condense at least a portion of it and form acondensed stream; and (b) said condensed stream is expanded to lowerpressure to form said liquefied natural gas stream; the improvementwherein (1) said natural gas stream is treated in one or more coolingsteps to partially condense it; (2) said partially condensed natural gasstream is separated to provide thereby a vapor stream and a first liquidstream; (3) said vapor stream is divided into at least a first gaseousstream and a second gaseous stream; (4) said first gaseous stream iscooled to condense substantially all of it and thereafter expanded to anintermediate pressure; (5) said second gaseous stream is expanded tosaid intermediate pressure; (6) said first liquid stream is expanded tosaid intermediate pressure; (7) said expanded substantially condensedgaseous first stream, said expanded gaseous second stream, and saidexpanded first liquid stream are directed into a distillation columnwherein said streams are separated into a volatile residue gas fractioncontaining a major portion of said methane and lighter components and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (8) said volatile residue gas fractionis cooled under pressure to condense at least a portion of it; (9) saidcondensed portion is divided into at least two portions to form therebysaid condensed stream and a second liquid stream; and (10) said secondliquid stream is directed into said distillation column as a top feedthereto.
 8. In a process for liquefying a natural gas stream containingmethane and heavier hydrocarbon components wherein (a) said natural gasstream is cooled under pressure to condense at least a portion of it andform a condensed stream; and (b) said condensed stream is expanded tolower pressure to form said liquefied natural gas stream; theimprovement wherein (1) said natural gas stream is treated in one ormore cooling steps to partially condense it; (2) said partiallycondensed natural gas stream is separated to provide thereby a vaporstream and a first liquid stream; (3) said vapor stream is divided intoat least a first gaseous stream and a second gaseous stream; (4) saidfirst gaseous stream is combined with at least a portion of said firstliquid stream, forming thereby a combined stream; (5) said combinedstream is cooled to condense substantially all of it and thereafterexpanded to an intermediate pressure; (6) said second gaseous stream isexpanded to said intermediate pressure; (7) any remaining portion ofsaid first liquid stream is expanded to said intermediate pressure; (8)said expanded substantially condensed combined stream, said expandedgaseous second stream, and said remaining portion of said first liquidstream are directed into a distillation column wherein said streams areseparated into a volatile residue gas fraction containing a majorportion of said methane and lighter components and a relatively lessvolatile fraction containing a major portion of said heavier hydrocarboncomponents; (9) said volatile residue gas fraction is cooled underpressure to condense at least a portion of it; (10) said condensedportion is divided into at least two portions to form thereby saidcondensed stream and a second liquid stream; and (11) said second liquidstream is directed into said distillation column as a top feed thereto.9. In a process for liquefying a natural gas stream containing methaneand heavier hydrocarbon components wherein (a) said natural gas streamis cooled under pressure to condense at least a portion of it and form acondensed stream; and (b) said condensed stream is expanded to lowerpressure to form said liquefied natural gas stream; the improvementwherein (1) said natural gas stream is treated in one or more coolingsteps; (2) said cooled natural gas stream is expanded to an intermediatepressure; (3) said expanded cooled natural gas stream is separated toprovide thereby a vapor stream and a liquid stream; (4) said liquidstream is expanded to a lower intermediate pressure; (5) said expandedliquid stream is directed into a distillation column wherein said streamis separated into a more volatile vapor distillation stream and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (6) said more volatile vapordistillation stream is combined with said vapor stream to form avolatile residue gas fraction containing a major portion of said methaneand lighter components; and (7) said volatile residue gas fraction iscooled under pressure to condense at least a portion of it and formthereby said condensed stream.
 10. In a process for liquefying a naturalgas stream containing methane and heavier hydrocarbon components wherein(a) said natural gas stream is cooled under pressure to condense atleast a portion of it and form a condensed stream; and (b) saidcondensed stream is expanded to lower pressure to form said liquefiednatural gas stream; the improvement wherein (1) said natural gas streamis treated in one or more cooling steps to partially condense it; (2)said partially condensed natural gas stream is separated to providethereby a first vapor stream and a first liquid stream; (3) said firstvapor stream is expanded to an intermediate pressure; (4) said expandedfirst vapor stream is separated to provide thereby a second vapor streamand a second liquid stream; (5) said second liquid stream is expanded toa lower intermediate pressure; (6) said first liquid stream is expandedto said lower intermediate pressure; (7) said expanded second liquidstream and said expanded first liquid stream are directed into adistillation column wherein said streams are separated into a morevolatile vapor distillation stream and a relatively less volatilefraction containing a major portion of said heavier hydrocarboncomponents; (8) said more volatile vapor distillation stream is combinedwith said second vapor stream to form a volatile residue gas fractioncontaining a major portion of said methane and lighter components; and(9) said volatile residue gas fraction is cooled under pressure tocondense at least a portion of it and form thereby said condensedstream.
 11. In a process for liquefying a natural gas stream containingmethane and heavier hydrocarbon components wherein (a) said natural gasstream is cooled under pressure to condense at least a portion of it andform a condensed stream; and (b) said condensed stream is expanded tolower pressure to form said liquefied natural gas stream; theimprovement wherein (1) said natural gas stream is treated in one ormore cooling steps; (2) said cooled natural gas stream is expanded to anintermediate pressure and thereafter directed into a contacting device,thereby forming a volatile residue gas fraction containing a majorportion of said methane and lighter components and a first liquidstream; (3) said first liquid stream is directed into a distillationcolumn wherein said stream is separated into a more volatile vapordistillation stream and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (4) said morevolatile vapor distillation stream is cooled sufficiently to condense atleast a part of it, thereby forming a second liquid stream; (5) at leasta portion of said expanded cooled natural gas stream is intimatelycontacted with at least part of said second liquid stream in saidcontacting device; and (6) said volatile residue gas fraction is cooledunder pressure to condense at least a portion of it and form therebysaid condensed stream.
 12. In a process for liquefying a natural gasstream containing methane and heavier hydrocarbon components wherein (a)said natural gas stream is cooled under pressure to condense at least aportion of it and form a condensed stream; and (b) said condensed streamis expanded to lower pressure to form said liquefied natural gas stream;the improvement wherein (1) said natural gas stream is treated in one ormore cooling steps to partially condense it; (2) said partiallycondensed natural gas stream is separated to provide thereby a vaporstream and a first liquid stream; (3) said vapor stream is expanded toan intermediate pressure and thereafter directed into a contactingdevice, thereby forming a volatile residue gas fraction containing amajor portion of said methane and lighter components and a second liquidstream; (4) said first liquid stream is expanded to said intermediatepressure; (5) said second liquid stream and said expanded first liquidstream are directed into a distillation column wherein said streams areseparated into a more volatile vapor distillation stream and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (6) said more volatile vapordistillation stream is cooled sufficiently to condense at least a partof it, thereby forming a third liquid stream; (7) at least a portion ofsaid expanded vapor stream is intimately contacted with at least part ofsaid third liquid stream in said contacting device; and (8) saidvolatile residue gas fraction is cooled under pressure to condense atleast a portion of it and form thereby said condensed stream.
 13. In aprocess for liquefying a natural gas stream containing methane andheavier hydrocarbon components wherein (a) said natural gas stream iscooled under pressure to condense at least a portion of it and form acondensed stream; and (b) said condensed stream is expanded to lowerpressure to form said liquefied natural gas stream; the improvementwherein (1) said natural gas stream is treated in one or more coolingsteps; (2) said cooled natural gas stream is expanded to an intermediatepressure and thereafter directed into a contacting device, therebyforming a first vapor stream and a first liquid stream; (3) said firstliquid stream is directed into a distillation column wherein said streamis separated into a more volatile vapor distillation stream and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (4) said more volatile vapordistillation stream is cooled sufficiently to condense at least a partof it, thereby forming a second vapor stream and a second liquid stream;(5) a portion of said second liquid stream is directed into saiddistillation column as a top feed thereto; (6) at least a portion ofsaid expanded cooled natural gas stream is intimately contacted with atleast part of the remaining portion of said second liquid stream in saidcontacting device; (7) said first vapor stream is combined with saidsecond vapor stream to form a volatile residue gas fraction containing amajor portion of said methane and lighter components; and (8) saidvolatile residue gas fraction is cooled under pressure to condense atleast a portion of it and form thereby said condensed stream.
 14. In aprocess for liquefying a natural gas stream containing methane andheavier hydrocarbon components wherein (a) said natural gas stream iscooled under pressure to condense at least a portion of it and form acondensed stream; and (b) said condensed stream is expanded to lowerpressure to form said liquefied natural gas stream; the improvementwherein (1) said natural gas stream is treated in one or more coolingsteps to partially condense it; (2) said partially condensed natural gasstream is separated to provide thereby a first vapor stream and a firstliquid stream; (3) said first vapor stream is expanded to anintermediate pressure and thereafter directed into a contacting device,thereby forming a second vapor stream and a second liquid stream; (4)said first liquid stream is expanded to said intermediate pressure; (5)said second liquid stream and said expanded first liquid stream aredirected into a distillation column wherein said streams are separatedinto a more volatile vapor distillation stream and a relatively lessvolatile fraction containing a major portion of said heavier hydrocarboncomponents; (6) said more volatile vapor distillation stream is cooledsufficiently to condense at least a part of it, thereby forming a thirdvapor stream and a third liquid stream; (7) a portion of said thirdliquid stream is directed into said distillation column as a top feedthereto; (8) at least a portion of said expanded first vapor stream isintimately contacted with at least part of the remaining portion of saidthird liquid stream in said contacting device; (9) said second vaporstream is combined with said third vapor stream to form a volatileresidue gas fraction containing a major portion of said methane andlighter components; and (10) said volatile residue gas fraction iscooled under pressure to condense at least a portion of it and formthereby said condensed stream.
 15. In a process for liquefying a naturalgas stream containing methane and heavier hydrocarbon components wherein(a) said natural gas stream is cooled under pressure to condense atleast a portion of it and form a condensed stream; and (b) saidcondensed stream is expanded to lower pressure to form said liquefiednatural gas stream; the improvement wherein (1) said natural gas streamis treated in one or more cooling steps; (2) said cooled natural gasstream is expanded to an intermediate pressure and thereafter directedinto a contacting device, thereby forming a volatile residue gasfraction containing a major portion of said methane and lightercomponents and a first liquid stream; (3) said first liquid stream isheated and thereafter directed into a distillation column wherein saidstream is separated into a more volatile vapor distillation stream and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (4) said more volatile vapordistillation stream is cooled sufficiently to condense at least a partof it, thereby forming a second liquid stream; (5) at least a portion ofsaid expanded cooled natural gas stream is intimately contacted with atleast part of said second liquid stream in said contacting device; and(6) said volatile residue gas fraction is cooled under pressure tocondense at least a portion of it and form thereby said condensedstream.
 16. In a process for liquefying a natural gas stream containingmethane and heavier hydrocarbon components wherein (a) said natural gasstream is cooled under pressure to condense at least a portion of it andform a condensed stream; and (b) said condensed stream is expanded tolower pressure to form said liquefied natural gas stream; theimprovement wherein (1) said natural gas stream is treated in one ormore cooling steps to partially condense it; (2) said partiallycondensed natural gas stream is separated to provide thereby a vaporstream and a first liquid stream; (3) said vapor stream is expanded toan intermediate pressure and thereafter directed into a contactingdevice, thereby forming a volatile residue gas fraction containing amajor portion of said methane and lighter components and a second liquidstream; (4) said second liquid stream is heated; (5) said first liquidstream is expanded to said intermediate pressure; (6) said heated secondliquid stream and said expanded first liquid stream are directed into adistillation column wherein said streams are separated into a morevolatile vapor distillation stream and a relatively less volatilefraction containing a major portion of said heavier hydrocarboncomponents; (7) said more volatile vapor distillation stream is cooledsufficiently to condense at least a part of it, thereby forming a thirdliquid stream; (8) at least a portion of said expanded vapor stream isintimately contacted with at least part of said third liquid stream insaid contacting device; and (9) said volatile residue gas fraction iscooled under pressure to condense at least a portion of it and formthereby said condensed stream.
 17. In a process for liquefying a naturalgas stream containing methane and heavier hydrocarbon components wherein(a) said natural gas stream is cooled under pressure to condense atleast a portion of it and form a condensed stream; and (b) saidcondensed stream is expanded to lower pressure to form said liquefiednatural gas stream; the improvement wherein (1) said natural gas streamis treated in one or more cooling steps; (2) said cooled natural gasstream is expanded to an intermediate pressure and thereafter directedinto a contacting device, thereby forming a first vapor stream and afirst liquid stream; (3) said first liquid stream is heated andthereafter directed into a distillation column wherein said stream isseparated into a more volatile vapor distillation stream and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (4) said more volatile vapordistillation stream is cooled sufficiently to condense at least a partof it, thereby forming a second vapor stream and a second liquid stream;(5) a portion of said second liquid stream is directed into saiddistillation column as a top feed thereto; (6) at least a portion ofsaid expanded cooled natural gas stream is intimately contacted with atleast part of the remaining portion of said second liquid stream in saidcontacting device; (7) said first vapor stream is combined with saidsecond vapor stream to form a volatile residue gas fraction containing amajor portion of said methane and lighter components; and (8) saidvolatile residue gas fraction is cooled under pressure to condense atleast a portion of it and form thereby said condensed stream.
 18. In aprocess for liquefying a natural gas stream containing methane andheavier hydrocarbon components wherein (a) said natural gas stream iscooled under pressure to condense at least a portion of it and form acondensed stream; and (b) said condensed stream is expanded to lowerpressure to form said liquefied natural gas stream; the improvementwherein (1) said natural gas stream is treated in one or more coolingsteps to partially condense it; (2) said partially condensed natural gasstream is separated to provide thereby a first vapor stream and a firstliquid stream; (3) said first vapor stream is expanded to anintermediate pressure and thereafter directed into a contacting device,thereby forming a second vapor stream and a second liquid stream; (4)said second liquid stream is heated; (5) said first liquid stream isexpanded to said intermediate pressure; (6) said heated second liquidstream and said expanded first liquid stream are directed into adistillation column wherein said streams are separated into a morevolatile vapor distillation stream and a relatively less volatilefraction containing a major portion of said heavier hydrocarboncomponents; (7) said more volatile vapor distillation stream is cooledsufficiently to condense at least a part of it, thereby forming a thirdvapor stream and a third liquid stream; (8) a portion of said thirdliquid stream is directed into said distillation column as a top feedthereto; (9) at least a portion of said expanded first vapor stream isintimately contacted with at least part of the remaining portion of saidthird liquid stream in said contacting device; (10) said second vaporstream is combined with said third vapor stream to form a volatileresidue gas fraction containing a major portion of said methane andlighter components; and (11) said volatile residue gas fraction iscooled under pressure to condense at least a portion of it and formthereby said condensed stream.
 19. The improvement according to claim 3,4, 5, 11, 12, 13, 14, 15, 16, 17 or 18 wherein said volatile residue gasfraction is compressed and thereafter cooled under pressure to condenseat least a portion of it and form thereby said condensed stream.
 20. Theimprovement according to claim 1 or 6 wherein (1) said volatile residuegas fraction is compressed and thereafter cooled under pressure tocondense at least a portion of it; and (2) said condensed portion isdivided into at least two portions to form thereby said condensed streamand said liquid stream.
 21. The improvement according to claim 2, 7, or8 wherein (1) said volatile residue gas fraction is compressed andthereafter cooled under pressure to condense at least a portion of it;and (2) said condensed portion is divided into at least two portions toform thereby said condensed stream and said second liquid stream. 22.The improvement according to claim 9 wherein said more volatile vapordistillation stream is compressed and thereafter combined with saidvapor stream to form said volatile residue gas fraction containing amajor portion of said methane and lighter components.
 23. Theimprovement according to claim 10 wherein said more volatile vapordistillation stream is compressed and thereafter combined with saidsecond vapor stream to form said volatile residue gas fractioncontaining a major portion of said methane and lighter components. 24.The improvement according to claim 3, 4, 5, 11, 12, 13, 14, 15, 16, 17or 18 wherein said volatile residue gas fraction is heated, compressed,and thereafter cooled under pressure to condense at least a portion ofit and form thereby said condensed stream.
 25. The improvement accordingto claim 1 or 6 wherein (1) said volatile residue gas fraction isheated, compressed, and thereafter cooled under pressure to condense atleast a portion of it; and (2) said condensed portion is divided into atleast two portions to form thereby said condensed stream and said liquidstream.
 26. The improvement according to claim 2, 7, or 8 wherein (1)said volatile residue gas fraction is heated, compressed, and thereaftercooled under pressure to condense at least a portion of it; and (2) saidcondensed portion is divided into at least two portions to form therebysaid condensed stream and said second liquid stream.
 27. The improvementaccording to claim 9 wherein said more volatile vapor distillationstream is heated, compressed, cooled, and thereafter combined with saidvapor stream to form said volatile residue gas fraction containing amajor portion of said methane and lighter components.
 28. Theimprovement according to claim 10 wherein said more volatile vapordistillation stream is heated, compressed, cooled, and thereaftercombined with said second vapor stream to form said volatile residue gasfraction containing a major portion of said methane and lightercomponents.
 29. The improvement according to claim 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 27, or 28 wherein saidvolatile residue gas fraction contains a major portion of said methane,lighter components, and C₂ components.
 30. The improvement according toclaim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 22,23, 27, or 28 wherein said volatile residue gas fraction contains amajor portion of said methane, lighter components, C₂ components, and C₃components.
 31. In an apparatus for the liquefaction of a natural gasstream containing methane and heavier hydrocarbon components, in saidapparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure; (2) second expansion means connected to saidsecond heat exchange means to receive said cooled natural gas stream andexpand it to an intermediate pressure; (3) a distillation columnconnected to receive said expanded cooled natural gas stream, with saiddistillation column adapted to separate said stream into a volatileresidue gas fraction containing a major portion of said methane andlighter components and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (4) said firstheat exchange means connected to said distillation column to receivesaid volatile residue gas fraction, with said first heat exchange meansadapted to cool said volatile residue gas fraction under pressure tocondense at least a portion of it; (5) dividing means connected to saidfirst heat exchange means to receive said condensed portion and divideit into at least two portions, forming thereby said condensed stream anda liquid stream, said dividing means being further connected to saiddistillation column to direct said liquid stream into said distillationcolumn as a top feed thereto; and (6) control means adapted to regulatethe quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 32. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure sufficiently to partially condense it; (2)separation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a vaporstream and a first liquid stream; (3) second expansion means connectedto said separation means to receive said vapor stream and expand it toan intermediate pressure; (4) third expansion means connected to saidseparation means to receive said first liquid stream and expand it tosaid intermediate pressure; (5) a distillation column connected toreceive said expanded vapor stream and said expanded first liquidstream, with said distillation column adapted to separate said streamsinto a volatile residue gas fraction containing a major portion of saidmethane and lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (6)said first heat exchange means connected to said distillation column toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it; (7) dividing meansconnected to said first heat exchange means to receive said condensedportion and divide it into at least two portions, forming thereby saidcondensed stream and a second liquid stream, said dividing means beingfurther connected to said distillation column to direct said secondliquid stream into said distillation column as a top feed thereto; and(8) control means adapted to regulate the quantities and temperatures ofsaid feed streams to said distillation column to maintain the overheadtemperature of said distillation column at a temperature whereby themajor portion of said heavier hydrocarbon components is recovered insaid relatively less volatile fraction.
 33. In an apparatus for theliquefaction of a natural gas stream containing methane and heavierhydrocarbon components, in said apparatus there being (a) one or morefirst heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure to condense at least aportion of it and form a condensed stream; and (b) first expansion meansconnected to said first heat exchange means to receive said condensedstream and expand it to lower pressure to form said liquefied naturalgas stream; the improvement wherein said apparatus includes (1) one ormore second heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure; (2) dividing meansconnected to said second heat exchange means to receive said coolednatural gas stream and divide it into at least a first gaseous streamand a second gaseous stream; (3) third heat exchange means connected tosaid dividing means to receive said first gaseous stream and to cool itsufficiently to substantially condense it; (4) second expansion meansconnected to said third heat exchange means to receive saidsubstantially condensed first gaseous stream and expand it to anintermediate pressure; (5) third expansion means connected to saiddividing means to receive said second gaseous stream and expand it tosaid intermediate pressure; (6) a distillation column connected toreceive said expanded substantially condensed first gaseous stream andsaid expanded second gaseous stream, with said distillation columnadapted to separate said streams into a volatile residue gas fractioncontaining a major portion of said methane and lighter components and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (7) said first heat exchange meansconnected to said distillation column to receive said volatile residuegas fraction, with said first heat exchange means adapted to cool saidvolatile residue gas fraction under pressure to condense at least aportion of it and form thereby said condensed stream; and (8) controlmeans adapted to regulate the quantities and temperatures of said feedstreams to said distillation column to maintain the overhead temperatureof said distillation column at a temperature whereby the major portionof said heavier hydrocarbon components is recovered in said relativelyless volatile fraction.
 34. In an apparatus for the liquefaction of anatural gas stream containing methane and heavier hydrocarboncomponents, in said apparatus there being (a) one or more first heatexchange means cooperatively connected to receive said natural gasstream and cool it under pressure to condense at least a portion of itand form a condensed stream; and (b) first expansion means connected tosaid first heat exchange means to receive said condensed stream andexpand it to lower pressure to form said liquefied natural gas stream;the improvement wherein said apparatus includes (1) one or more secondheat exchange means cooperatively connected to receive said natural gasstream and cool it under pressure sufficiently to partially condense it;(2) separation means connected to said second heat exchange means toreceive said partially condensed natural gas stream and separate it intoa vapor stream and a liquid stream; (3) dividing means connected to saidseparation means to receive said vapor stream and divide it into atleast a first gaseous stream and a second gaseous stream; (4) third heatexchange means connected to said dividing means to receive said firstgaseous stream and to cool it sufficiently to substantially condense it;(5) second expansion means connected to said third heat exchange meansto receive said substantially condensed first gaseous stream and expandit to an intermediate pressure; (6) third expansion means connected tosaid dividing means to receive said second gaseous stream and expand itto said intermediate pressure; (7) fourth expansion means connected tosaid separation means to receive said liquid stream and expand it tosaid intermediate pressure; (8) a distillation column connected toreceive said expanded substantially condensed first gaseous stream, saidexpanded second gaseous stream, and said expanded liquid stream, withsaid distillation column adapted to separate said streams into avolatile residue gas fraction containing a major portion of said methaneand lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (9)said first heat exchange means connected to said distillation column toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it and form thereby saidcondensed stream; and (10) control means adapted to regulate thequantities and temperatures of said feed streams to said distillationcolumn to maintain the overhead temperature of said distillation columnat a temperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 35.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure sufficiently to partially condense it; (2) separationmeans connected to said second heat exchange means to receive saidpartially condensed natural gas stream and separate it into a vaporstream and a liquid stream; (3) dividing means connected to saidseparation means to receive said vapor stream and divide it into atleast a first gaseous stream and a second gaseous stream; (4) combiningmeans connected to said dividing means and to said separation means toreceive said first gaseous stream and at least a portion of said liquidstream and combine them into a combined stream; (5) third heat exchangemeans connected to said combining means to receive said combined streamand to cool it sufficiently to substantially condense it; (6) secondexpansion means connected to said third heat exchange means to receivesaid substantially condensed combined stream and expand it to anintermediate pressure; (7) third expansion means connected to saiddividing means to receive said second gaseous stream and expand it tosaid intermediate pressure; (8) fourth expansion means connected to saidseparation means to receive any remaining portion of said liquid streamand expand it to said intermediate pressure; (9) a distillation columnconnected to receive said expanded substantially condensed combinedstream, said expanded second gaseous stream, and said expanded remainingportion of said liquid stream, with said distillation column adapted toseparate said streams into a volatile residue gas fraction containing amajor portion of said methane and lighter components and a relativelyless volatile fraction containing a major portion of said heavierhydrocarbon components; (10) said first heat exchange means connected tosaid distillation column to receive said volatile residue gas fraction,with said first heat exchange means adapted to cool said volatileresidue gas fraction under pressure to condense at least a portion of itand form thereby said condensed stream; and (11) control means adaptedto regulate the quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 36. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure; (2) first dividing means connected to saidsecond heat exchange means to receive said cooled natural gas stream anddivide it into at least a first gaseous stream and a second gaseousstream; (3) third heat exchange means connected to said first dividingmeans to receive said first gaseous stream and to cool it sufficientlyto substantially condense it; (4) second expansion means connected tosaid third heat exchange means to receive said substantially condensedfirst gaseous stream and expand it to an intermediate pressure; (5)third expansion means connected to said first dividing means to receivesaid second gaseous stream and expand it to said intermediate pressure;(6) a distillation column connected to receive said expandedsubstantially condensed first gaseous stream and said expanded secondgaseous stream, with said distillation column adapted to separate saidstreams into a volatile residue gas fraction containing a major portionof said methane and lighter components and a relatively less volatilefraction containing a major portion of said heavier hydrocarboncomponents; (7) said first heat exchange means connected to saiddistillation column to receive said volatile residue gas fraction, withsaid first heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it; (8) seconddividing means connected to said first heat exchange means to receivesaid condensed portion and divide it into at least two portions, formingthereby said condensed stream and a liquid stream, said second dividingmeans being further connected to said distillation column to direct saidliquid stream into said distillation column as a top feed thereto; and(9) control means adapted to regulate the quantities and temperatures ofsaid feed streams to said distillation column to maintain the overheadtemperature of said distillation column at a temperature whereby themajor portion of said heavier hydrocarbon components is recovered insaid relatively less volatile fraction.
 37. In an apparatus for theliquefaction of a natural gas stream containing methane and heavierhydrocarbon components, in said apparatus there being (a) one or morefirst heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure to condense at least aportion of it and form a condensed stream; and (b) first expansion meansconnected to said first heat exchange means to receive said condensedstream and expand it to lower pressure to form said liquefied naturalgas stream; the improvement wherein said apparatus includes (1) one ormore second heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure sufficiently to partiallycondense it; (2) separation means connected to said second heat exchangemeans to receive said partially condensed natural gas stream andseparate it into a vapor stream and a first liquid stream; (3) firstdividing means connected to said separation means to receive said vaporstream and divide it into at least a first gaseous stream and a secondgaseous stream; (4) third heat exchange means connected to said firstdividing means to receive said first gaseous stream and to cool itsufficiently to substantially condense it; (5) second expansion meansconnected to said third heat exchange means to receive saidsubstantially condensed first gaseous stream and expand it to anintermediate pressure; (6) third expansion means connected to said firstdividing means to receive said second gaseous stream and expand it tosaid intermediate pressure; (7) fourth expansion means connected to saidseparation means to receive said first liquid stream and expand it tosaid intermediate pressure; (8) a distillation column connected toreceive said expanded substantially condensed first gaseous stream, saidexpanded second gaseous stream, and said expanded first liquid stream,with said distillation column adapted to separate said streams into avolatile residue gas fraction containing a major portion of said methaneand lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (9)said first heat exchange means connected to said distillation column toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it; (10) second dividingmeans connected to said first heat exchange means to receive saidcondensed portion and divide it into at least two portions, formingthereby said condensed stream and a second liquid stream, said seconddividing means being further connected to said distillation column todirect said second liquid stream into said distillation column as a topfeed thereto; and (11) control means adapted to regulate the quantitiesand temperatures of said feed streams to said distillation column tomaintain the overhead temperature of said distillation column at atemperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 38.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure sufficiently to partially condense it; (2) separationmeans connected to said second heat exchange means to receive saidpartially condensed natural gas stream and separate it into a vaporstream and a first liquid stream; (3) first dividing means connected tosaid separation means to receive said vapor stream and divide it into atleast a first gaseous stream and a second gaseous stream; (4) combiningmeans connected to said first dividing means and to said separationmeans to receive said first gaseous stream and at least a portion ofsaid first liquid stream and combine them into a combined stream; (5)third heat exchange means connected to said combining means to receivesaid combined stream and to cool it sufficiently to substantiallycondense it; (6) second expansion means connected to said third heatexchange means to receive said substantially condensed combined streamand expand it to an intermediate pressure; (7) third expansion meansconnected to said first dividing means to receive said second gaseousstream and expand it to said intermediate pressure; (8) fourth expansionmeans connected to said separation means to receive any remainingportion of said first liquid stream and expand it to said intermediatepressure; (9) a distillation column connected to receive said expandedsubstantially condensed combined stream, said expanded second gaseousstream, and said expanded remaining portion of said first liquid stream,with said distillation column adapted to separate said streams into avolatile residue gas fraction containing a major portion of said methaneand lighter components and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (10)said first heat exchange means connected to said distillation column toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it; (11) second dividingmeans connected to said first heat exchange means to receive saidcondensed portion and divide it into at least two portions, formingthereby said condensed stream and a second liquid stream, said seconddividing means being further connected to said distillation column todirect said second liquid stream into said distillation column as a topfeed thereto; and (12) control means adapted to regulate the quantitiesand temperatures of said feed streams to said distillation column tomaintain the overhead temperature of said distillation column at atemperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 39.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure; (2) second expansion means connected to said second heatexchange means to receive said cooled natural gas stream and expand itto an intermediate pressure; (3) separation means connected to saidsecond expansion means to receive said expanded cooled natural gasstream and separate it into a vapor stream and a liquid stream; (4)third expansion means connected to said separation means to receive saidliquid stream and expand it to a lower intermediate pressure; (5) adistillation column connected to receive said expanded liquid stream,with said distillation column adapted to separate said stream into amore volatile vapor distillation stream and a relatively less volatilefraction containing a major portion of said heavier hydrocarboncomponents; (6) combining means connected to said separation means andsaid distillation column to receive said vapor stream and said morevolatile vapor distillation stream and combine them to form a volatileresidue gas fraction containing a major portion of said methane andlighter components; (7) said first heat exchange means connected to saidcombining means to receive said volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (8) control means adapted to regulatethe quantity and temperature of said feed stream to said distillationcolumn to maintain the overhead temperature of said distillation columnat a temperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 40.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure sufficiently to partially condense it; (2) firstseparation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said first separation means to receive said first vaporstream and expand it to an intermediate pressure; (4) second separationmeans connected to said second expansion means to receive said expandedfirst vapor stream and separate it into a second vapor stream and asecond liquid stream; (5) third expansion means connected to said secondseparation means to receive said second liquid stream and expand it to alower intermediate pressure; (6) fourth expansion means connected tosaid first separation means to receive said first liquid stream andexpand it to said lower intermediate pressure; (7) a distillation columnconnected to receive said expanded second liquid stream and saidexpanded first liquid stream, with said distillation column adapted toseparate said streams into a more volatile vapor distillation stream anda relatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (8) combining means connected to saidsecond separation means and said distillation column to receive saidsecond vapor stream and said more volatile vapor distillation stream andcombine them to form a volatile residue gas fraction containing a majorportion of said methane and lighter components; (9) said first heatexchange means connected to said combining means to receive saidvolatile residue gas fraction, with said first heat exchange meansadapted to cool said volatile residue gas fraction under pressure tocondense at least a portion of it and form thereby said condensedstream; and (10) control means adapted to regulate the quantities andtemperatures of said feed streams to said distillation column tomaintain the overhead temperature of said distillation column at atemperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 41.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure; (2) second expansion means connected to said second heatexchange means to receive said cooled natural gas stream and expand itto an intermediate pressure; (3) contacting and separating meansconnected to receive said expanded cooled natural gas stream, with saidcontacting and separating means containing at least one contactingdevice to commingle liquid and vapor and including separating means toseparate the vapor and liquid after commingling to form a volatileresidue gas fraction containing a major portion of said methane andlighter components and a first liquid stream; (4) a distillation columnconnected to receive said first liquid stream, with said distillationcolumn adapted to separate said stream into a more volatile vapordistillation stream and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (5) third heatexchange means connected to said distillation column to receive saidmore volatile vapor distillation stream and cool it sufficiently tocondense at least a part of it, thereby forming a second liquid stream;(6) said contacting and separating means being further connected to saidthird heat exchange means to receive said second liquid stream so thatat least a portion of said expanded cooled natural gas stream isintimately contacted with at least part of said second liquid stream insaid contacting device; (7) said first heat exchange means connected tosaid contacting and separating means to receive said volatile residuegas fraction, with said first heat exchange means adapted to cool saidvolatile residue gas fraction under pressure to condense at least aportion of it and form thereby said condensed stream; and (8) controlmeans adapted to regulate the quantities and temperatures of said feedstreams to said contacting and separating means and said distillationcolumn to maintain the overhead temperatures of said contacting andseparating means and said distillation column at temperatures wherebythe major portion of said heavier hydrocarbon components is recovered insaid relatively less volatile fraction.
 42. In an apparatus for theliquefaction of a natural gas stream containing methane and heavierhydrocarbon components, in said apparatus there being (a) one or morefirst heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure to condense at least aportion of it and form a condensed stream; and (b) first expansion meansconnected to said first heat exchange means to receive said condensedstream and expand it to lower pressure to form said liquefied naturalgas stream; the improvement wherein said apparatus includes (1) one ormore second heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure sufficiently to partiallycondense it; (2) separation means connected to said second heat exchangemeans to receive said partially condensed natural gas stream andseparate it into a vapor stream and a first liquid stream; (3) secondexpansion means connected to said separation means to receive said vaporstream and expand it to an intermediate pressure; (4) contacting andseparating means connected to receive said expanded vapor stream, withsaid contacting and separating means containing at least one contactingdevice to commingle liquid and vapor and including separating means toseparate the vapor and liquid after commingling to form a volatileresidue gas fraction containing a major portion of said methane andlighter components and a second liquid stream; (5) third expansion meansconnected to said separation means to receive said first liquid streamand expand it to said intermediate pressure; (6) a distillation columnconnected to receive said second liquid stream and said expanded firstliquid stream, with said distillation column adapted to separate saidstreams into a more volatile vapor distillation stream and a relativelyless volatile fraction containing a major portion of said heavierhydrocarbon components; (7) third heat exchange means connected to saiddistillation column to receive said more volatile vapor distillationstream and cool it sufficiently to condense at least a part of it,thereby forming a third liquid stream; (8) said contacting andseparating means being further connected to said third heat exchangemeans to receive said third liquid stream so that at least a portion ofsaid expanded vapor stream is intimately contacted with at least part ofsaid third liquid stream in said contacting device; (9) said first heatexchange means connected to said contacting and separating means toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it and form thereby saidcondensed stream; and (10) control means adapted to regulate thequantities and temperatures of said feed streams to said contacting andseparating means and said distillation column to maintain the overheadtemperatures of said contacting and separating means and saiddistillation column at temperatures whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 43. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure; (2) second expansion means connected to saidsecond heat exchange means to receive said cooled natural gas stream andexpand it to an intermediate pressure; (3) contacting and separatingmeans connected to receive said expanded cooled natural gas stream, withsaid contacting and separating means containing at least one contactingdevice to commingle liquid and vapor and including separating means toseparate the vapor and liquid after commingling to form a first vaporstream and a first liquid stream; (4) a distillation column connected toreceive said first liquid stream, with said distillation column adaptedto separate said stream into a more volatile vapor distillation streamand a relatively less volatile fraction containing a major portion ofsaid heavier hydrocarbon components; (5) third heat exchange meansconnected to said distillation column to receive said more volatilevapor distillation stream and cool it sufficiently to condense at leasta part of it; (6) separation means connected to said third heat exchangemeans to receive said cooled more volatile vapor distillation stream andseparate it into a second vapor stream and a second liquid stream; (7)dividing means connected to said separation means to receive said secondliquid stream and to divide it into at least a first portion and asecond portion, said dividing means being further connected to saiddistillation column to supply said first portion of said second liquidstream to said distillation column as a top feed thereto; (8) saidcontacting and separating means being further connected to said dividingmeans to receive said second portion of said second liquid stream sothat at least a portion of said expanded cooled natural gas stream isintimately contacted with at least part of said second portion of saidsecond liquid stream in said contacting device; (9) combining meansconnected to said contacting and separating means and said separationmeans to receive said first vapor stream and said second vapor streamand combine them to form a volatile residue gas fraction containing amajor portion of said methane and lighter components; (10) said firstheat exchange means connected to said combining means to receive saidvolatile residue gas fraction, with said first heat exchange meansadapted to cool said volatile residue gas fraction under pressure tocondense at least a portion of it and form thereby said condensedstream; and (11) control means adapted to regulate the quantities andtemperatures of said feed streams to said contacting and separatingmeans and said distillation column to maintain the overhead temperaturesof said contacting and separating means and said distillation column attemperatures whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 44.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure sufficiently to partially condense it; (2) firstseparation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said first separation means to receive said first vaporstream and expand it to an intermediate pressure; (4) contacting andseparating means connected to receive said expanded first vapor stream,with said contacting and separating means containing at least onecontacting device to commingle liquid and vapor and including separatingmeans to separate the vapor and liquid after commingling to form asecond vapor stream and a second liquid stream; (5) third expansionmeans connected to said separation means to receive said first liquidstream and expand it to said intermediate pressure; (6) a distillationcolumn connected to receive said second liquid stream and said expandedfirst liquid stream, with said distillation column adapted to separatesaid streams into a more volatile vapor distillation stream and arelatively less volatile fraction containing a major portion of saidheavier hydrocarbon components; (7) third heat exchange means connectedto said distillation column to receive said more volatile vapordistillation stream and cool it sufficiently to condense at least a partof it; (8) second separation means connected to said third heat exchangemeans to receive said cooled more volatile vapor distillation stream andseparate it into a third vapor stream and a third liquid stream; (9)dividing means connected to said second separation means to receive saidthird liquid stream and to divide it into at least a first portion and asecond portion, said dividing means being further connected to saiddistillation column to supply said first portion of said third liquidstream to said distillation column as a top feed thereto; (10) saidcontacting and separating means being further connected to said dividingmeans to receive said second portion of said third liquid stream so thatat least a portion of said expanded first vapor stream is intimatelycontacted with at least part of said second portion of said third liquidstream in said contacting device; (11) combining means connected to saidcontacting and separating means and said separation means to receivesaid second vapor stream and said third vapor stream and combine them toform a volatile residue gas fraction containing a major portion of saidmethane and lighter components; (12) said first heat exchange meansconnected to said combining means to receive said volatile residue gasfraction, with said first heat exchange means adapted to cool saidvolatile residue gas fraction under pressure to condense at least aportion of it and form thereby said condensed stream; and (13) controlmeans adapted to regulate the quantities and temperatures of said feedstreams to said contacting and separating means and said distillationcolumn to maintain the overhead temperatures of said contacting andseparating means and said distillation column at temperatures wherebythe major portion of said heavier hydrocarbon components is recovered insaid relatively less volatile fraction.
 45. In an apparatus for theliquefaction of a natural gas stream containing methane and heavierhydrocarbon components, in said apparatus there being (a) one or morefirst heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure to condense at least aportion of it and form a condensed stream; and (b) first expansion meansconnected to said first heat exchange means to receive said condensedstream and expand it to lower pressure to form said liquefied naturalgas stream; the improvement wherein said apparatus includes (1) one ormore second heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure; (2) second expansionmeans connected to said second heat exchange means to receive saidcooled natural gas stream and expand it to an intermediate pressure; (3)contacting and separating means connected to receive said expandedcooled natural gas stream, with said contacting and separating meanscontaining at least one contacting device to commingle liquid and vaporand including separating means to separate the vapor and liquid aftercommingling to form a volatile residue gas fraction containing a majorportion of said methane and lighter components and a first liquidstream; (4) third heat exchange means connected to said contacting andseparating means to receive said first liquid stream and heat it; (5) adistillation column connected to receive said heated first liquidstream, with said distillation column adapted to separate said streaminto a more volatile vapor distillation stream and a relatively lessvolatile fraction containing a major portion of said heavier hydrocarboncomponents; (6) fourth heat exchange means connected to saiddistillation column to receive said more volatile vapor distillationstream and cool it sufficiently to condense at least a part of it,thereby forming a second liquid stream; (7) said contacting andseparating means being further connected to said fourth heat exchangemeans to receive said second liquid stream so that at least a portion ofsaid expanded cooled natural gas stream is intimately contacted with atleast part of said second liquid stream in said contacting device; (8)said first heat exchange means connected to said contacting andseparating means to receive said volatile residue gas fraction, withsaid first heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (9) control means adapted to regulatethe quantities and temperatures of said feed streams to said contactingand separating means and said distillation column to maintain theoverhead temperatures of said contacting and separating means and saiddistillation column at temperatures whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 46. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure sufficiently to partially condense it; (2)separation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said separation means to receive said first vapor streamand expand it to an intermediate pressure; (4) contacting and separatingmeans connected to receive said expanded first vapor stream, with saidcontacting and separating means containing at least one contactingdevice to commingle liquid and vapor and including separating means toseparate the vapor and liquid after commingling to form a volatileresidue gas fraction containing a major portion of said methane andlighter components and a second liquid stream; (5) third heat exchangemeans connected to said contacting and separating means to receive saidsecond liquid stream and heat it; (6) third expansion means connected tosaid separation means to receive said first liquid stream and expand itto said intermediate pressure; (7) a distillation column connected toreceive said heated second liquid stream and said expanded first liquidstream, with said distillation column adapted to separate said streamsinto a more volatile vapor distillation stream and a relatively lessvolatile fraction containing a major portion of said heavier hydrocarboncomponents; (8) fourth heat exchange means connected to saiddistillation column to receive said more volatile vapor distillationstream and cool it sufficiently to condense at least a part of it,thereby forming a third liquid stream; (9) said contacting andseparating means being further connected to said fourth heat exchangemeans to receive said third liquid stream so that at least a portion ofsaid expanded first vapor stream is intimately contacted with at leastpart of said third liquid stream in said contacting device; (10) saidfirst heat exchange means connected to said contacting and separatingmeans to receive said volatile residue gas fraction, with said firstheat exchange means adapted to cool said volatile residue gas fractionunder pressure to condense at least a portion of it and form therebysaid condensed stream; and (11) control means adapted to regulate thequantities and temperatures of said feed streams to said contacting andseparating means and said distillation column to maintain the overheadtemperatures of said contacting and separating means and saiddistillation column at temperatures whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 47. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure; (2) second expansion means connected to saidsecond heat exchange means to receive said cooled natural gas stream andexpand it to an intermediate pressure; (3) contacting and separatingmeans connected to receive said expanded cooled natural gas stream, withsaid contacting and separating means containing at least one contactingdevice to commingle liquid and vapor and including separating means toseparate the vapor and liquid after commingling to form a first vaporstream and a first liquid stream; (4) third heat exchange meansconnected to said contacting and separating means to receive said firstliquid stream and heat it; (5) a distillation column connected toreceive said heated first liquid stream, with said distillation columnadapted to separate said stream into a more volatile vapor distillationstream and a relatively less volatile fraction containing a majorportion of said heavier hydrocarbon components; (6) fourth heat exchangemeans connected to said distillation column to receive said morevolatile vapor distillation stream and cool it sufficiently to condenseat least a part of it; (7) separation means connected to said fourthheat exchange means to receive said cooled more volatile vapordistillation stream and separate it into a second vapor stream and asecond liquid stream; (8) dividing means connected to said separationmeans to receive said second liquid stream and to divide it into atleast a first portion and a second portion, said dividing means beingfurther connected to said distillation column to supply said firstportion of said second liquid stream to said distillation column as atop feed thereto; (9) said contacting and separating means being furtherconnected to said dividing means to receive said second portion of saidsecond liquid stream so that at least a portion of said expanded coolednatural gas stream is intimately contacted with at least part of saidsecond portion of said second liquid stream in said contacting device;(10) combining means connected to said contacting and separating meansand said separation means to receive said first vapor stream and saidsecond vapor stream and combine them to form a volatile residue gasfraction containing a major portion of said methane and lightercomponents; (11) said first heat exchange means connected to saidcombining means to receive said volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (12) control means adapted toregulate the quantities and temperatures of said feed streams to saidcontacting and separating means and said distillation column to maintainthe overhead temperatures of said contacting and separating means andsaid distillation column at temperatures whereby the major portion ofsaid heavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 48. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure sufficiently to partially condense it; (2) firstseparation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said first separation means to receive said first vaporstream and expand it to an intermediate pressure; (4) contacting andseparating means connected to receive said expanded first vapor stream,with said contacting and separating means containing at least onecontacting device to commingle liquid and vapor and including separatingmeans to separate the vapor and liquid after commingling to form asecond vapor stream and a second liquid stream; (5) third heat exchangemeans connected to said contacting and separating means to receive saidsecond liquid stream and heat it; (6) third expansion means connected tosaid separation means to receive said first liquid stream and expand itto said intermediate pressure; (7) a distillation column connected toreceive said heated second liquid stream and said expanded first liquidstream, with said distillation column adapted to separate said streamsinto a more volatile vapor distillation stream and a relatively lessvolatile fraction containing a major portion of said heavier hydrocarboncomponents; (8) fourth heat exchange means connected to saiddistillation column to receive said more volatile vapor distillationstream and cool it sufficiently to condense at least a part of it; (9)second separation means connected to said fourth heat exchange means toreceive said cooled more volatile vapor distillation stream and separateit into a third vapor stream and a third liquid stream; (10) dividingmeans connected to said second separation means to receive said thirdliquid stream and to divide it into at least a first portion and asecond portion, said dividing means being further connected to saiddistillation column to supply said first portion of said third liquidstream to said distillation column as a top feed thereto; (11) saidcontacting and separating means being further connected to said dividingmeans to receive said second portion of said third liquid stream so thatat least a portion of said expanded first vapor stream is intimatelycontacted with at least part of said second portion of said third liquidstream in said contacting device; (12) combining means connected to saidcontacting and separating means and said second separation means toreceive said second vapor stream and said third vapor stream and combinethem to form a volatile residue gas fraction containing a major portionof said methane and lighter components; (13) said first heat exchangemeans connected to said combining means to receive said volatile residuegas fraction, with said first heat exchange means adapted to cool saidvolatile residue gas fraction under pressure to condense at least aportion of it and form thereby said condensed stream; and (14) controlmeans adapted to regulate the quantities and temperatures of said feedstreams to said contacting and separating means and said distillationcolumn to maintain the overhead temperatures of said contacting andseparating means and said distillation column at temperatures wherebythe major portion of said heavier hydrocarbon components is recovered insaid relatively less volatile fraction.
 49. In an apparatus for theliquefaction of a natural gas stream containing methane and heavierhydrocarbon components, in said apparatus there being (a) one or morefirst heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure to condense at least aportion of it and form a condensed stream; and (b) first expansion meansconnected to said first heat exchange means to receive said condensedstream and expand it to lower pressure to form said liquefied naturalgas stream; the improvement wherein said apparatus includes (1) one ormore second heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure; (2) second expansionmeans connected to said second heat exchange means to receive saidcooled natural gas stream and expand it to an intermediate pressure; (3)a distillation column connected to receive said expanded cooled naturalgas stream, with said distillation column adapted to separate saidstream into a more volatile vapor distillation stream and a relativelyless volatile fraction containing a major portion of said heavierhydrocarbon components; (4) vapor withdrawing means connected to saiddistillation column to receive a vapor distillation stream from a regionof said distillation column below said expanded cooled natural gasstream; (5) third heat exchange means connected to said vaporwithdrawing means to receive said vapor distillation stream and cool itsufficiently to condense at least a part of it; (6) separation meansconnected to said third heat exchange means to receive said cooled vapordistillation stream and separate it into a vapor stream and a liquidstream; (7) said distillation column being further connected to saidseparation means to receive said liquid stream so that at least aportion of said expanded cooled natural gas stream is intimatelycontacted with at least part of said liquid stream in said distillationcolumn; (8) combining means connected to said distillation column andsaid separation means to receive said more volatile vapor distillationstream and said vapor stream and combine them to form a volatile residuegas fraction containing a major portion of said methane and lightercomponents; (9) said first heat exchange means connected to saidcombining means to receive said volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (10) control means adapted toregulate the quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 50. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure sufficiently to partially condense it; (2) firstseparation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said first separation means to receive said first vaporstream and expand it to an intermediate pressure; (4) third expansionmeans connected to said first separation means to receive said firstliquid stream and expand it to said intermediate pressure; (5) adistillation column connected to receive said expanded first vaporstream and said expanded first liquid stream, with said distillationcolumn adapted to separate said streams into a more volatile vapordistillation stream and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (6) vaporwithdrawing means connected to said distillation column to receive avapor distillation stream from a region of said distillation columnbelow said expanded first vapor stream; (7) third heat exchange meansconnected to said vapor withdrawing means to receive said vapordistillation stream and cool it sufficiently to condense at least a partof it; (8) second separation means connected to said third heat exchangemeans to receive said cooled vapor distillation stream and separate itinto a second vapor stream and a second liquid stream; (9) saiddistillation column being further connected to said second separationmeans to receive said second liquid stream so that at least a portion ofsaid expanded first vapor stream is intimately contacted with at leastpart of said second liquid stream in said distillation column; (10)combining means connected to said distillation column and said secondseparation means to receive said more volatile vapor distillation streamand said second vapor stream and combine them to form a volatile residuegas fraction containing a major portion of said methane and lightercomponents; (11) said first heat exchange means connected to saidcombining means to receive said volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (12) control means adapted toregulate the quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 51. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure; (2) second expansion means connected to saidsecond heat exchange means to receive said cooled natural gas stream andexpand it to an intermediate pressure; (3) a distillation columnconnected to receive said expanded cooled natural gas stream, with saiddistillation column adapted to separate said stream into a more volatilevapor distillation stream and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (4)vapor withdrawing means connected to said distillation column to receivea vapor distillation stream from a region of said distillation columnbelow said expanded cooled natural gas stream; (5) third heat exchangemeans connected to said vapor withdrawing means to receive said vapordistillation stream and cool it sufficiently to condense at least a partof it; (6) separation means connected to said third heat exchange meansto receive said cooled vapor distillation stream and separate it into avapor stream and a liquid stream; (7) dividing means connected to saidseparation means to receive said liquid stream and to divide it into atleast a first portion and a second portion, said dividing means beingfurther connected to said distillation column to supply said firstportion of said liquid stream to said distillation column at a feedlocation in substantially the same region wherein said vapordistillation stream is withdrawn; (8) said distillation column beingfurther connected to said dividing means to receive said second portionof said liquid stream so that at least a portion of said expanded coolednatural gas stream is intimately contacted with at least part of saidsecond portion of said liquid stream in said distillation column; (9)combining means connected to said distillation column and saidseparation means to receive said more volatile vapor distillation streamand said vapor stream and combine them to form a volatile residue gasfraction containing a major portion of said methane and lightercomponents; (10) said first heat exchange means connected to saidcombining means to receive said volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (11) control means adapted toregulate the quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 52. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure sufficiently to partially condense it; (2) firstseparation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said first separation means to receive said first vaporstream and expand it to an intermediate pressure; (4) third expansionmeans connected to said first separation means to receive said firstliquid stream and expand it to said intermediate pressure; (5) adistillation column connected to receive said expanded first vaporstream and said expanded first liquid stream, with said distillationcolumn adapted to separate said streams into a more volatile vapordistillation stream and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (6) vaporwithdrawing means connected to said distillation column to receive avapor distillation stream from a region of said distillation columnbelow said expanded first vapor stream; (7) third heat exchange meansconnected to said vapor withdrawing means to receive said vapordistillation stream and cool it sufficiently to condense at least a partof it; (8) second separation means connected to said third heat exchangemeans to receive said cooled vapor distillation stream and separate itinto a second vapor stream and a second liquid stream; (9) dividingmeans connected to said second separation means to receive said secondliquid stream and to divide it into at least a first portion and asecond portion, said dividing means being further connected to saiddistillation column to supply said first portion of said second liquidstream to said distillation column at a feed location in substantiallythe same region wherein said vapor distillation stream is withdrawn;(10) said distillation column being further connected to said dividingmeans to receive said second portion of said second liquid stream sothat at least a portion of said expanded first vapor stream isintimately contacted with at least part of said second portion of saidsecond liquid stream in said distillation column; (11) combining meansconnected to said distillation column and said separation means toreceive said more volatile vapor distillation stream and said secondvapor stream and combine them to form a volatile residue gas fractioncontaining a major portion of said methane and lighter components; (12)said first heat exchange means connected to said combining means toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it and form thereby saidcondensed stream; and (13) control means adapted to regulate thequantities and temperatures of said feed streams to said distillationcolumn to maintain the overhead temperature of said distillation columnat a temperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 53.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure; (2) second expansion means connected to said second heatexchange means to receive said cooled natural gas stream and expand itto an intermediate pressure; (3) a distillation column connected toreceive said expanded cooled natural gas stream, with said distillationcolumn adapted to separate said stream into a more volatile vapordistillation stream and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (4) vaporwithdrawing means connected to said distillation column to receive avapor distillation stream from a region of said distillation columnbelow said expanded cooled natural gas stream; (5) third heat exchangemeans connected to said vapor withdrawing means to receive said vapordistillation stream and cool it sufficiently to condense at least a partof it; (6) separation means connected to said third heat exchange meansto receive said cooled vapor distillation stream and separate it into avapor stream and a liquid stream; (7) said distillation column beingfurther connected to said separation means to receive said liquid streamso that at least a portion of said expanded cooled natural gas stream isintimately contacted with at least part of said liquid stream in saiddistillation column; (8) liquid withdrawing means connected to saiddistillation column to receive a liquid distillation stream from aregion of said distillation column above that of said vapor withdrawingmeans; (9) fourth heat exchange means connected to said liquidwithdrawing means to receive said liquid distillation stream and heatit, said fourth heat exchange means being further connected to saiddistillation column to supply said heated liquid distillation stream tosaid distillation column at a location below that of said vaporwithdrawing means; (10) combining means connected to said distillationcolumn and said separation means to receive said more volatile vapordistillation stream and said vapor stream and combine them to form avolatile residue gas fraction containing a major portion of said methaneand lighter components; (11) said first heat exchange means connected tosaid combining means to receive said volatile residue gas fraction, withsaid first heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (12) control means adapted toregulate the quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 54. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure sufficiently to partially condense it; (2) firstseparation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said first separation means to receive said first vaporstream and expand it to an intermediate pressure; (4) third expansionmeans connected to said first separation means to receive said firstliquid stream and expand it to said intermediate pressure; (5) adistillation column connected to receive said expanded first vaporstream and said expanded first liquid stream, with said distillationcolumn adapted to separate said streams into a more volatile vapordistillation stream and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (6) vaporwithdrawing means connected to said distillation column to receive avapor distillation stream from a region of said distillation columnbelow said expanded first vapor stream; (7) third heat exchange meansconnected to said vapor withdrawing means to receive said vapordistillation stream and cool it sufficiently to condense at least a partof it; (8) second separation means connected to said third heat exchangemeans to receive said cooled vapor distillation stream and separate itinto a second vapor stream and a second liquid stream; (9) saiddistillation column being further connected to said second separationmeans to receive said second liquid stream so that at least a portion ofsaid expanded first vapor stream is intimately contacted with at leastpart of said second liquid stream in said distillation column; (10)liquid withdrawing means connected to said distillation column toreceive a liquid distillation stream from a region of said distillationcolumn above that of said vapor withdrawing means; (11) fourth heatexchange means connected to said liquid withdrawing means to receivesaid liquid distillation stream and heat it, said fourth heat exchangemeans being further connected to said distillation column to supply saidheated liquid distillation stream to said distillation column at alocation below that of said vapor withdrawing means; (12) combiningmeans connected to said distillation column and said second separationmeans to receive said more volatile vapor distillation stream and saidsecond vapor stream and combine them to form a volatile residue gasfraction containing a major portion of said methane and lightercomponents; (13) said first heat exchange means connected to saidcombining means to receive said volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said volatile residue gasfraction under pressure to condense at least a portion of it and formthereby said condensed stream; and (14) control means adapted toregulate the quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 55. In an apparatus for the liquefaction of a naturalgas stream containing methane and heavier hydrocarbon components, insaid apparatus there being (a) one or more first heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure to condense at least a portion of it and form a condensedstream; and (b) first expansion means connected to said first heatexchange means to receive said condensed stream and expand it to lowerpressure to form said liquefied natural gas stream; the improvementwherein said apparatus includes (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure; (2) second expansion means connected to saidsecond heat exchange means to receive said cooled natural gas stream andexpand it to an intermediate pressure; (3) a distillation columnconnected to receive said expanded cooled natural gas stream, with saiddistillation column adapted to separate said stream into a more volatilevapor distillation stream and a relatively less volatile fractioncontaining a major portion of said heavier hydrocarbon components; (4)vapor withdrawing means connected to said distillation column to receivea vapor distillation stream from a region of said distillation columnbelow said expanded cooled natural gas stream; (5) third heat exchangemeans connected to said vapor withdrawing means to receive said vapordistillation stream and cool it sufficiently to condense at least a partof it; (6) separation means connected to said third heat exchange meansto receive said cooled vapor distillation stream and separate it into avapor stream and a liquid stream; (7) dividing means connected to saidseparation means to receive said liquid stream and to divide it into atleast a first portion and a second portion, said dividing means beingfurther connected to said distillation column to supply said firstportion of said liquid stream to said distillation column at a feedlocation in substantially the same region wherein said vapordistillation stream is withdrawn; (8) said distillation column beingfurther connected to said dividing means to receive said second portionof said liquid stream so that at least a portion of said expanded coolednatural gas stream is intimately contacted with at least part of saidsecond portion of said liquid stream in said distillation column; (9)liquid withdrawing means connected to said distillation column toreceive a liquid distillation stream from a region of said distillationcolumn above that of said vapor withdrawing means; (10) fourth heatexchange means connected to said liquid withdrawing means to receivesaid liquid distillation stream and heat it, said fourth heat exchangemeans being further connected to said distillation column to supply saidheated liquid distillation stream to said distillation column at alocation below that of said vapor withdrawing means; (11) combiningmeans connected to said distillation column and said separation means toreceive said more volatile vapor distillation stream and said vaporstream and combine them to form a volatile residue gas fractioncontaining a major portion of said methane and lighter components; (12)said first heat exchange means connected to said combining means toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it and form thereby saidcondensed stream; and (13) control means adapted to regulate thequantities and temperatures of said feed streams to said distillationcolumn to maintain the overhead temperature of said distillation columnat a temperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 56.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus includes (1) one or more second heat exchange meanscooperatively connected to receive said natural gas stream and cool itunder pressure sufficiently to partially condense it; (2) firstseparation means connected to said second heat exchange means to receivesaid partially condensed natural gas stream and separate it into a firstvapor stream and a first liquid stream; (3) second expansion meansconnected to said first separation means to receive said first vaporstream and expand it to an intermediate pressure; (4) third expansionmeans connected to said first separation means to receive said firstliquid stream and expand it to said intermediate pressure; (5) adistillation column connected to receive said expanded first vaporstream and said expanded first liquid stream, with said distillationcolumn adapted to separate said streams into a more volatile vapordistillation stream and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (6) vaporwithdrawing means connected to said distillation column to receive avapor distillation stream from a region of said distillation columnbelow said expanded first vapor stream; (7) third heat exchange meansconnected to said vapor withdrawing means to receive said vapordistillation stream and cool it sufficiently to condense at least a partof it; (8) second separation means connected to said third heat exchangemeans to receive said cooled vapor distillation stream and separate itinto a second vapor stream and a second liquid stream; (9) dividingmeans connected to said second separation means to receive said secondliquid stream and to divide it into at least a first portion and asecond portion, said dividing means being further connected to saiddistillation column to supply said first portion of said second liquidstream to said distillation column at a feed location in substantiallythe same region wherein said vapor distillation stream is withdrawn;(10) said distillation column being further connected to said dividingmeans to receive said second portion of said second liquid stream sothat at least a portion of said expanded first vapor stream isintimately contacted with at least part of said second portion of saidsecond liquid stream in said distillation column; (11) liquidwithdrawing means connected to said distillation column to receive aliquid distillation stream from a region of said distillation columnabove that of said vapor withdrawing means; (12) fourth heat exchangemeans connected to said liquid withdrawing means to receive said liquiddistillation stream and heat it, said fourth heat exchange means beingfurther connected to said distillation column to supply said heatedliquid distillation stream to said distillation column at a locationbelow that of said vapor withdrawing means; (13) combining meansconnected to said distillation column and said second separation meansto receive said more volatile vapor distillation stream and said secondvapor stream and combine them to form a volatile residue gas fractioncontaining a major portion of said methane and lighter components; (14)said first heat exchange means connected to said combining means toreceive said volatile residue gas fraction, with said first heatexchange means adapted to cool said volatile residue gas fraction underpressure to condense at least a portion of it and form thereby saidcondensed stream; and (15) control means adapted to regulate thequantities and temperatures of said feed streams to said distillationcolumn to maintain the overhead temperature of said distillation columnat a temperature whereby the major portion of said heavier hydrocarboncomponents is recovered in said relatively less volatile fraction. 57.In an apparatus for the liquefaction of a natural gas stream containingmethane and heavier hydrocarbon components, in said apparatus therebeing (a) one or more first heat exchange means cooperatively connectedto receive said natural gas stream and cool it under pressure tocondense at least a portion of it and form a condensed stream; and (b)first expansion means connected to said first heat exchange means toreceive said condensed stream and expand it to lower pressure to formsaid liquefied natural gas stream; the improvement wherein saidapparatus consists essentially of (1) one or more second heat exchangemeans cooperatively connected to receive said natural gas stream andcool it under pressure; (2) second expansion means connected to saidsecond heat exchange means to receive said cooled natural gas stream andexpand it to an intermediate pressure; (3) a distillation columnconnected to receive said expanded cooled natural gas stream, with saiddistillation column adapted to separate said stream into a volatileresidue gas fraction containing a major portion of said methane andlighter components and a relatively less volatile fraction containing amajor portion of said heavier hydrocarbon components; (4) said firstheat exchange means connected to said distillation column to receivesaid volatile residue gas fraction, with said first heat exchange meansadapted to cool said volatile residue gas fraction under pressure tocondense at least a portion of it and form thereby said condensedstream; and (5) control means adapted to regulate the quantity andtemperature of said feed stream to said distillation column to maintainthe overhead temperature of said distillation column at a temperaturewhereby the major portion of said heavier hydrocarbon components isrecovered in said relatively less volatile fraction.
 58. In an apparatusfor the liquefaction of a natural gas stream containing methane andheavier hydrocarbon components, in said apparatus there being (a) one ormore first heat exchange means cooperatively connected to receive saidnatural gas stream and cool it under pressure to condense at least aportion of it and form a condensed stream; and (b) first expansion meansconnected to said first heat exchange means to receive said condensedstream and expand it to lower pressure to form said liquefied naturalgas stream; the improvement wherein said apparatus consists essentiallyof (1) one or more second heat exchange means cooperatively connected toreceive said natural gas stream and cool it under pressure sufficientlyto partially condense it; (2) separation means connected to said secondheat exchange means to receive said partially condensed natural gasstream and separate it into a vapor stream and a liquid stream; (3)second expansion means connected to said separation means to receivesaid vapor stream and expand it to an intermediate pressure; (4) thirdexpansion means connected to said separation means to receive saidliquid stream and expand it to said intermediate pressure; (5) adistillation column connected to receive said expanded vapor stream andsaid expanded liquid stream, with said distillation column adapted toseparate said streams into a volatile residue gas fraction containing amajor portion of said methane and lighter components and a relativelyless volatile fraction containing a major portion of said heavierhydrocarbon components; (6) said first heat exchange means connected tosaid distillation column to receive said volatile residue gas fraction,with said first heat exchange means adapted to cool said volatileresidue gas fraction under pressure to condense at least a portion of itand form thereby said condensed stream; and (7) control means adapted toregulate the quantities and temperatures of said feed streams to saiddistillation column to maintain the overhead temperature of saiddistillation column at a temperature whereby the major portion of saidheavier hydrocarbon components is recovered in said relatively lessvolatile fraction.
 59. The improvement according to claim 33, 34, 35,57, or 58 wherein said apparatus includes (1) compressing meansconnected to said distillation column to receive said volatile residuegas fraction and compress it; and (2) said first heat exchange meansconnected to said compressing means to receive said compressed volatileresidue gas fraction, with said first heat exchange means adapted tocool said compressed volatile residue gas fraction under pressure tocondense at least a portion of it and form thereby said condensedstream.
 60. The improvement according to claim. 31 wherein saidapparatus includes (1) compressing means connected to said distillationcolumn to receive said volatile residue gas fraction and compress it;(2) said first heat exchange means connected to said compressing meansto receive said compressed volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said compressed volatileresidue gas fraction under pressure to condense at least a portion ofit; and (3) said dividing means connected to said first heat exchangemeans to receive said condensed portion and divide it into at least twoportions, forming thereby said condensed stream and said liquid stream,said dividing means being further connected to said distillation columnto direct said liquid stream into said distillation column as a top feedthereto.
 61. The improvement according to claim 32 wherein saidapparatus includes (1) compressing means connected to said distillationcolumn to receive said volatile residue gas fraction and compress it;(2) said first heat exchange means connected to said compressing meansto receive said compressed volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said compressed volatileresidue gas fraction under pressure to condense at least a portion ofit; and (3) said dividing means connected to said first heat exchangemeans to receive said condensed portion and divide it into at least twoportions, forming thereby said condensed stream and said second liquidstream, said dividing means being further connected to said distillationcolumn to direct said second liquid stream into said distillation columnas a top feed thereto.
 62. The improvement according to claim 36 whereinsaid apparatus includes (1) compressing means connected to saiddistillation column to receive said volatile residue gas fraction andcompress it; (2) said first heat exchange means connected to saidcompressing means to receive said compressed volatile residue gasfraction, with said first heat exchange means adapted to cool saidcompressed volatile residue gas fraction under pressure to condense atleast a portion of it; and (3) said second dividing means connected tosaid first heat exchange means to receive said condensed portion anddivide it into at least two portions, forming thereby said condensedstream and said liquid stream, said second dividing means being furtherconnected to said distillation column to direct said liquid stream intosaid distillation column as a top feed thereto.
 63. The improvementaccording to claim 37 or 38 wherein said apparatus includes (1)compressing means connected to said distillation column to receive saidvolatile residue gas fraction and compress it; (2) said first heatexchange means connected to said compressing means to receive saidcompressed volatile residue gas fraction, with said first heat exchangemeans adapted to cool said compressed volatile residue gas fractionunder pressure to condense at least a portion of it; and (3) said seconddividing means connected to said first heat exchange means to receivesaid condensed portion and divide it into at least two portions, formingthereby said condensed stream and said second liquid stream, said seconddividing means being further connected to said distillation column todirect said second liquid stream into said distillation column as a topfeed thereto.
 64. The improvement according to claim 39 wherein saidapparatus includes (1) compressing means connected to said distillationcolumn to receive said more volatile vapor distillation stream andcompress it; and (2) said combining means connected to said separationmeans and said compressing means to receive said vapor stream and saidcompressed more volatile vapor distillation stream and combine them toform said volatile residue gas fraction containing a major portion ofsaid methane and lighter components.
 65. The improvement according toclaim 40 wherein said apparatus includes (1) compressing means connectedto said distillation column to receive said more volatile vapordistillation stream and compress it; and (2) said combining meansconnected to said second separation means and said compressing means toreceive said second vapor stream and said compressed more volatile vapordistillation stream and combine them to form a volatile residue gasfraction containing a major portion of said methane and lightercomponents.
 66. The improvement according to claim 41, 42, 45, or 46wherein said apparatus includes (1) compressing means connected to saidcontacting and separating means to receive said volatile residue gasfraction and compress it; and (2) said first heat exchange meansconnected to said compressing means to receive said compressed volatileresidue gas fraction, with said first heat exchange means adapted tocool said compressed volatile residue gas fraction under pressure tocondense at least a portion of it and form thereby said condensedstream.
 67. The improvement according to claim 43, 44, 47, 48, 49, 50,51, 52, 53, 54, 55, or 56 wherein said apparatus includes (1)compressing means connected to said combining means to receive saidvolatile residue gas fraction and compress it; and (2) said first heatexchange means connected to said compressing means to receive saidcompressed volatile residue gas fraction, with said first heat exchangemeans adapted to cool said compressed volatile residue gas fractionunder pressure to condense at least a portion of it and form therebysaid condensed stream.
 68. The improvement according to claim 33, 34,35, 57, or 58 wherein said apparatus includes (1) heating meansconnected to said distillation column to receive said volatile residuegas fraction and heat it; (2) compressing means connected to saidheating means to receive said heated volatile residue gas fraction andcompress it; and (3) said first heat exchange means connected to saidcompressing means to receive said compressed heated volatile residue gasfraction, with said first heat exchange means adapted to cool saidcompressed heated volatile residue gas fraction under pressure tocondense at least a portion of it and form thereby said condensedstream.
 69. The improvement according to claim 31 wherein said apparatusincludes (1) heating means connected to said distillation column toreceive said volatile residue gas fraction and heat it; (2) compressingmeans connected to said heating means to receive said heated volatileresidue gas fraction and compress it; (3) said first heat exchange meansconnected to said compressing means to receive said compressed heatedvolatile residue gas fraction, with said first heat exchange meansadapted to cool said compressed heated volatile residue gas fractionunder pressure to condense at least a portion of it; and (4) saiddividing means connected to said first heat exchange means to receivesaid condensed portion and divide it into at least two portions, formingthereby said condensed stream and said liquid stream, said dividingmeans being further connected to said distillation column to direct saidliquid stream into said distillation column as a top feed thereto. 70.The improvement according to claim 32 wherein said apparatus includes(1) heating means connected to said distillation column to receive saidvolatile residue gas fraction and heat it; (2) compressing meansconnected to said heating means to receive said heated volatile residuegas fraction and compress it; (3) said first heat exchange meansconnected to said compressing means to receive said compressed heatedvolatile residue gas fraction, with said first heat exchange meansadapted to cool said compressed heated volatile residue gas fractionunder pressure to condense at least a portion of it; and (4) saiddividing means connected to said first heat exchange means to receivesaid condensed portion and divide it into at least two portions, formingthereby said condensed stream and said second liquid stream, saiddividing means being further connected to said distillation column todirect said second liquid stream into said distillation column as a topfeed thereto.
 71. The improvement according to claim 36 wherein saidapparatus includes (1) heating means connected to said distillationcolumn to receive said volatile residue gas fraction and heat it; (2)compressing means connected to said heating means to receive said heatedvolatile residue gas fraction and compress it; (3) said first heatexchange means connected to said compressing means to receive saidcompressed heated volatile residue gas fraction, with said first heatexchange means adapted to cool said compressed heated volatile residuegas fraction under pressure to condense at least a portion of it; and(4) said second dividing means connected to said first heat exchangemeans to receive said condensed portion and divide it into at least twoportions, forming thereby said condensed stream and said liquid stream,said second dividing means being further connected to said distillationcolumn to direct said liquid stream into said distillation column as atop feed thereto.
 72. The improvement according to claim 37 or 38wherein said apparatus includes (1) heating means connected to saiddistillation column to receive said volatile residue gas fraction andheat it; (2) compressing means connected to said heating means toreceive said heated volatile residue gas fraction and compress it; (3)said first heat exchange means connected to said compressing means toreceive said compressed heated volatile residue gas fraction, with saidfirst heat exchange means adapted to cool said compressed heatedvolatile residue gas fraction under pressure to condense at least aportion of it; and (4) said second dividing means connected to saidfirst heat exchange means to receive said condensed portion and divideit into at least two portions, forming thereby said condensed stream andsaid second liquid stream, said second dividing means being furtherconnected to said distillation column to direct said second liquidstream into said distillation column as a top feed thereto.
 73. Theimprovement according to claim 39 wherein said apparatus includes (1)heating means connected to said distillation column to receive said morevolatile vapor distillation stream and heat it; (2) compressing meansconnected to said heating means to receive said heated more volatilevapor distillation stream and compress it; (3) cooling means connectedto said compressing means to receive said compressed heated morevolatile vapor distillation stream and cool it; (4) said combining meansconnected to said separation means and said cooling means to receivesaid vapor stream and said cooled compressed more volatile vapordistillation stream and combine them to form a volatile residue gasfraction containing a major portion of said methane and lightercomponents.
 74. The improvement according to claim 40 wherein saidapparatus includes (1) heating means connected to said distillationcolumn to receive said more volatile vapor distillation stream and heatit; (2) compressing means connected to said heating means to receivesaid heated more volatile vapor distillation stream and compress it; (3)cooling means connected to said compressing means to receive saidcompressed heated more volatile vapor distillation stream and cool it;(4) said combining means connected to said second separation means andsaid cooling means to receive said second vapor stream and said cooledcompressed more volatile vapor distillation stream and combine them toform a volatile residue gas fraction containing a major portion of saidmethane and lighter components.
 75. The improvement according to claim41, 42, 45, or 46 wherein said apparatus includes (1) heating meansconnected to said contacting and separating means to receive saidvolatile residue gas fraction and heat it; (2) compressing meansconnected to said heating means to receive said heated volatile residuegas fraction and compress it; and (3) said first heat exchange meansconnected to said compressing means to receive said compressed heatedvolatile residue gas fraction, with said first heat exchange meansadapted to cool said compressed heated volatile residue gas fractionunder pressure to condense at least a portion of it and form therebysaid condensed stream.
 76. The improvement according to claim 43, 44,47, 48, 49, 50, 51, 52, 53, 54, 55, or 56 wherein said apparatusincludes (1) heating means connected to said combining means to receivesaid volatile residue gas fraction and heat it; (2) compressing meansconnected to said heating means to receive said heated volatile residuegas fraction and compress it; and (3) said first heat exchange meansconnected to said compressing means to receive said compressed heatedvolatile residue gas fraction, with said first heat exchange meansadapted to cool said compressed heated volatile residue gas fractionunder pressure to condense at least a portion of it and form therebysaid condensed stream.
 77. The improvement according to claim 31, 32,33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,51, 52, 53, 54, 55, 56, 57, 58, 60, 61, 62, 64, 65, 69, 70, 71, 73 or74, Wherein said volatile residue gas fraction contains a major portionof said methane, lighter components, and C₂ components.
 78. Theimprovement according to claim 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41,42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58,60, 61, 62, 64, 65, 69, 70, 71, 73 or 74, wherein said volatile residuegas fraction contains a major portion of said methane, lightercomponents, C₂ components, and C₃ components.
 79. The improvementaccording to claim 19 wherein said volatile residue gas fractioncontains a major portion of said methane, lighter components, and C₂components.
 80. The improvement according to claim 20 wherein saidvolatile residue gas fraction contains a major portion of said methane,lighter components, and C₂ components.
 81. The improvement according toclaim 21 wherein said volatile residue gas fraction contains a majorportion of said methane, lighter components, and C₂ components.
 82. Theimprovement according to claim 24 wherein said volatile residue gasfraction contains a major portion of said methane, lighter components,and C₂ components.
 83. The improvement according to claim 25 whereinsaid volatile residue gas fraction contains a major portion of saidmethane, lighter components, and C₂ components.
 84. The improvementaccording to claim 26 wherein said volatile residue gas fractioncontains a major portion of said methane, lighter components, and C₂components.
 85. The improvement according to claim 19 wherein saidvolatile residue gas fraction contains a major portion of said methane,lighter components, C₂ components, and C₃ components.
 86. Theimprovement according to claim 20 wherein said volatile residue gasfraction contains a major portion of said methane, lighter components,C₂ components, and C₃ components.
 87. The improvement according to claim21 wherein said volatile residue gas fraction contains a major portionof said methane, lighter components, C₂ components, and C₃ components.88. The improvement according to claim 24 wherein said volatile residuegas fraction contains a major portion of said methane, lightercomponents, C₂ components, and C₃ components.
 89. The improvementaccording to claim 25 wherein said volatile residue gas fractioncontains a major portion of said methane, lighter components, C₂components, and C₃ components.
 90. The improvement according to claim 26wherein said volatile residue gas fraction contains a major portion ofsaid methane, lighter components, C₂ components, and C₃ components. 91.The improvement according to claim 59 wherein said volatile residue gasfraction contains a major portion of said methane, lighter components,and C₂ components.
 92. The improvement according to claim 63 whereinsaid volatile residue gas fraction contains a major portion of saidmethane, lighter components, and C₂ components.
 93. The improvementaccording to claim 65 wherein said volatile residue gas fractioncontains a major portion of said methane, lighter components, and C₂components.
 94. The improvement according to claim 67 wherein saidvolatile residue gas fraction contains a major portion of said methane,lighter components, and C₂ components.
 95. The improvement according toclaim 68 wherein said volatile residue gas fraction contains a majorportion of said methane, lighter components, and C₂ components.
 96. Theimprovement according to claim 72 wherein said volatile residue gasfraction contains a major portion of said methane, lighter components,and C₂ components.
 97. The improvement according to claim 75 whereinsaid volatile residue gas fraction contains a major portion of saidmethane, lighter components, and C₂ components.
 98. The improvementaccording to claim 76 wherein said volatile residue gas fractioncontains a major portion of said methane, lighter components, and C₂components.